What if IronMan joined in to help Thor and Captain America kill Thanos with Stormbreaker during Endgame. Would they have been successful or fail but with a different result?
Did you mean in the Wakanda battle in Infinity War?
If so, they might have still fail if Thanos manage to acquire all the stones. Tony took a beating against Thanos on Titan, so the results could still be the same. Doctor Strange still might have given up the Time Stone too. It is hard to tell, but the addition of Iron Man would not guarantee success.
I mean the battle in Endgame. Thor stops Thanos from getting the Gauntlet and almost successfully kills him with the extra help of Captain America before Thanos breaks free and knocks them both out.
