My friend and I have been playing Borderlands 2 online on the Xbox for months. Today he's coming here at my place and we want to have a session together. If I make him log with his account on my Xbox, will he be able to use his character?
If the operation is the same as on PC your characters are saved online. It's necessary to launch the game (and the game session) on the account who hosted for the first time the game, otherwise you will spawn in the first mission of the game (with your character).