Onslaught could simply use his reality warping powers to completely destroy team 2 before any of them could even hurt him. He could destroy the professor and then his team would be back if that is any consolation. It really isn't fair having a reality warper on one side like this, and honestly Onslaught is OP when fighting anybody who can't.
Wolverine, Iron Man, and Hulk would be fighting for team 2 because of Professor X. So the combined force of Hulk, Iron Man, Sentry, Wolverine, and Superman will be more than enough to defeat Captain Marvel, Black Adam, and Onslaught