A/N: Slightly AU. This story is basically what would have happened if Heimdall had sent Thor and Loki along with the Hulk to Earth using the Bifrost. Also, this is my first time writing Fanfiction, sooooo, you've been warned.
Prologue
"I promise you, brother. The sun will shine on us again," Loki stated as he advanced slowly towards Thanos with his arm outstretched and the Tesseract in his palm.
"Your optimism is misplaced, Asgardian," Thanos scoffed.
Loki smirked as he said, "For one thing, I'm not Asgardian. And, for another, we have a Hulk."
Suddenly, the Hulk barreled into Thanos with a roar. For a moment it seemed as if the Hulk had the upper hand. Then, Thanos suddenly struck the Hulk. Hard. The Hulk reeled back in pain and let out a cry before hurling himself again at the Titan. However, Thanos blocked every single blow that was coming to him.
The two fought viciously before Thanos slammed the Hulk into the ground in a final blow. The Hulk lay unmoving on the floor.
Thor and Loki stood, shocked. With the last of his energy, Heimdall sent a rainbow light surging through the ship and the brothers and the Hulk were soon flying through the cosmos towards Earth, where they would hopefully warn everyone about what has transpired and what is going to happen.
Thanos turned to Heimdall.
"That was a mistake," he said, almost disdainfully before stabbing Heimdall in the chest.