Oncest in 2020? More likely than you thought.
More seriously, I found back my love for this ship and found there was a cruel lack of content for it, so here is my addition after rewatching the movie three hours ago.
Watching his family going away didn't do anything to him. If he had to be honest, he even despised them, especially his mother who never gave a damn about him up until he was making money. He could do perfectly fine without them. After all, it not like they were ever there for him in the past. Actually, he wasn't even close to being surprised that they were going away and that he was now back on the case "disappointment".
He couldn't care less about them.
Then it was the turn of the Brown Bar-ba-loots, the Humming-Fish and Swomee-Swans to go away. Even if he didn't care much about them, something deep in him was actually saddened to see them go. Something deep in him remembered the memories he had with them and was devastated to see them go. But it was still something really small in him.
He could live without them, it's not like he had much time for them before in the first place.
Then it was the Lorax time to go and this actually surprised him, he wasn't excepting for the furry peanut to go away too. He wasn't sure what he was actually expecting, maybe for him to bother him and haunt him until he died? But not to lift himself in the sky by the seat of his pants. This had shocked him and had surprisingly a lot of effect on him more than he would admit it. He had gotten used to the Lorax over the years.
But he could survive without him, right?
He fell to his knee, looking at the ring of stone left behind. Then everything finally sank in: he had nothing left. No family, as much as he despised them it was still a presence around. No more little furry friend, even if he hadn't had the time to be with them in the last years. No more Lorax to tell him he was doing it all wrong. No more business. No more money. No more... anything. He was left alone.
He then remembers about Oncie, panic building up in him. He had him left, right? Or had he already left him behind? He suddenly got up, ready to sprint inside his gigantic factory to find his younger self, but stop when he saw him at the bottom of the stair.
Once-ler was looking somewhere far in the horizon, where all his little furry friend had gone. He was crying, even if he didn't know it himself, his gaze looking around them to take in the disaster around them. The one they had caused, no... the one he had caused himself because of his Greed.
Greed-ler ran to his younger self, startling him out from his trance. He quickly threw his sunglasses away, taking Once-ler in his arm, tightly keeping him near him, hiding in the crook of his neck. He could hear his top hat falling in the stairs. He wouldn't let go. He couldn't let go. He was so scared he would leave him too if he did it. He couldn't let him go. He was all he had left. He was what he needed the most. He was all he cared about in this big empty place.
Oncie was surprised when he heard quiet sob coming from the Greed-ler. Even that panicked and desperate expression he made when he was ready to run inside had surprised him. He hugged him back, hiding against his shoulder, unable to keep looking at what was left of the valley, crying silently with him. He then could start hearing the plea from his older self.
Never in his life had Greed-ler plea or begged, people were maybe doing this towards him, but he would never have done it. But here he was, begging for the Once-ler not to leave him, that he needed him at his side, that they were meant to stay together. "I love you, please don't leave me" he whispered faintly, Oncie nearly missing it.
The Once-ler hugged him closer to him, his hiding his own crying mess in the crook of a neck identical to his. "Of course I won't, I love you, I can't leave you" he said back, trying to keep in the sobs escaping him.
He knew the best choice would probably to go and find somewhere better to live. He knew he shouldn't be staying with the one who had destroyed the whole place (even if in a way it was also his fault). He knew he would have a better quality of life elsewhere. But how could he when he had since a long time already fallen in love with the Greed-ler? How could he go away and leave the person he needed the most, but also needed him the most.
He was murmuring word of reassurance, telling him he wouldn't go away, that he would stay with him no matter what. That they both brought it upon themselves and that they would endure the consequence together. That he didn't really have anywhere to go anyway.
They were slowly sinking to there knee, trying to calm themselves, but how could they? They were instead clinging to each other as if their lives depended on it, as if one of them would suddenly disappear and leave the other one alone.
No, the Greed-ler cared about him. He couldn't live without him. He couldn't survive without him.
Oncie was all he had left and he wouldn't let that go for anything in the world.
Later, they both saw the factory being taken down. It was hard for both of them, really hard.
The only thing left was a house they could both live in, far away in this wasteland. That too was also hard, but they were able to get used to it. It wasn't really as if they had any other choice.
Times were sometimes rough. Things were sometimes going worse for them. But it was alright, it never killed the love they had for each other. It was something they couldn't lose, it was all they really had left, with each other.
They did make a promise, that even if this love was to die, they would stick together, because they would still need each other, because they would still be all they had left. Surprisingly enough, it was the optimistic Oncie who suggested that promise, sending Greed-ler in a pit of anxiety. It took him a couple of weeks to reassure his older self he still loved him, that it was just a hypothetical scenario. None the least, the man had been the sweetest and the kindness he could to him, scared he wouldn't love him anymore if he was acting a little more like himself.
They also went over, maybe thousand of time (Oncie had stop counting), who was at fault for this mess. It was in times where Greed would be the most depressed and apologising over and over for what he brought upon them. And over and over again would Once-ler tell him it was also his fault, it was both theirs to carry, not only him. After all, the Lorax had brought him to meet his future self so he could stop him, but instead, he had fell head over heels in love with the Greed-ler and didn't stop him. Plus, if he had stayed in his time, he would still have become Greed.
They would sometime find a way to get inside the new city. Never for more than a couple of hours. It was always to get some goods they needed to survive. Because what they were using was pretty much that, enough to survive. Luckily enough, and by some miracle maybe, they were still able to have some water good enough to drink out of the city.
At some point, a routine had settled on both of them, rarely broken by problems they accoutered. They would sometime get in fights, staying in different rooms for a couple of hours before the need to be with each other was too strong. They couldn't stay in bad term for long, as often those arguments were childish or irrelevant, it was all quickly forgotten.
Some would probably ask: why did none of them try to grow a truffula tree since they had a seed? It was probably a mixture of both shame over what they did and a lack of believing it would even work. They actually did try a handful of time, but it never worked. Well, what could actually grow in such a bad environment? The sun was never out, the air was poisonous and water was a luxury in the wasteland.
Then that routine they had was broken by the visit of a boy, growing some hope inside them as he was asking about trees. Maybe there was a way to reverse this mess?
Greed-ler choice to tell him what he did to this place and from where it all started. Sometimes, Once-ler would remind him of something he was missing, always sitting out of viewing range, near the planked window. Always whispering some comment under his breath, Greed needing to keep from laughing or getting frustrated as they tried to keep the impression they were one person.
They gave all their hope in that boy when they gave him the seed, both silhouette looking at him go back to the city, hopeful smile on their faces. They did all they could, now they needed to wait and see how things would go.
It took some years before they could see strong changes in the wasteland, but little by little it was coming. They knew things were getting better as the boy was often coming to visit them and updating them on all they were doing.
As the grass was slowly getting back and small truffula trees were growing, they slowly could relax. They never totally forgave themselves and each other for what they did, but at least now they knew it would be okay. They supposed not many people had the chance to see their biggest mistake being taken care of when they were still alive. Though they had to admit, they were both starting to get old.
But growing old wasn't that bad, especially since they didn't have to worry anymore. Maybe they wouldn't be in contact with anyone else than the boy and the returning creature, but it was fine.
They had each other and their love, that was all they needed.