The Pushover—
Everyone always thinks that they can tell Albus what to do. It's true, to an extent. He likes being told exactly how things are going to go because he hates having to make decisions. There will always be a "wrong choice" and a "right choice", and that scares him. What if he picks the wrong one?
Regret is one of the hardest things to live with. And the people who say "no regrets" are usually the ones with the most of them. So he lets people tell him what to do, he lets them influence him. He knows he probably shouldn't but he does anyway, because it's just easier.
And Fred tells him jokes, and Roxie lets him play with her potions set, and Louis draws him. No one has a problem with good ol' Al.
But it bothers him too. Because sometimes he just wants to fight with someone. To yell and to scream and to banter back and forth.
So when he blows up on Lily's little friend he feels ashamed and cruel, like he often imagines that James feels when he's played a prank on an innocent person. But the little spitfire yells and kicks and spits insults right back at him.
The rest of the school is in shock. Albus Potter doesn't get along with someone?
But he revels in it, enjoying it. And he knows that ever since he met Lacey Sinclair, his life has never been the same. Now he's not a pushover, he's the one pushing.