I suck at summaries.

Alex Rider is now a criminal, and also an expert on terrorists. When the Avengers need help on something he's a little too close to he's dumped at their feet, (practically) tied with a bow. Except they're not the conniving agents he's come to expect but more of a strange family, and when they start to uncover his numerous secrets things are really gonna get explosive...

Alex Rider has never been a normal teenager, now he's even less of one. When he's once again attacked by Scorpia he is put under the protection of the Avengers. What will they think of him? Has he finally found a place to belong or will he still be an outsider around those so similar to himself? Alex Rider, Avengers Xover ABANDONED

They both worked as top agents in the spy network. Naturally, they knew each other. (features FemAlex)

Alex knew everything about the inner workings of the world. After being thrust back into the game of spies and assassins, he is damn near the best agent in the free world. But, he's about to find out that there's a whole world that he knows nothing about, one with gods, monsters, super-soldiers, and techno-marvels. And if he's going to survive, he'll have to (re)learn how to adapt.