The team to save the world if I had a fantasy team would go as followed and the would be called The Gods of Men.. Don't judge the name. They are more focused on saving the world not coming up with a name.
third round: Superman
When you think about it, he is pretty much a God. He can fly, shoot lasers from his eyes, freeze things with his breath, super human strength, the power to rebuild the great wall of china with his vision(even though that movie was lame as heck), and so much more! Super man is damn near invincible! And with some of the other people on my team, he will be a good fit.
second round: Deadpool
Deadpool is the best mutant in the X Men universe in my opinion. He has mutant healing, has the ability to kill the entire MCU. Something that hasn't been done before and i don't will be done another time. He is just a power house. He has the power of the 4th wall. Don't ever underestimate the 4th wall. He can also just kick ass. With his swords and some guns, There isn't anyone who can stop him in my opinion.
first round: Scarlet Witch
Scarlet witch is a very dangerous player in the MCU. She really does have a power that can't be beat. The power to warp reality. With this she can do what ever she sees fit. She also can project hex spears. She can control other peoples mind and use them for her own will. So she could just wreck anything that stood in her way
Leader: One above all
This was tough. It was either him or the presence from D.C but I went with the one above all because he can beat every single marvel being single handedly. He is THE God of the marvel Universe so why wouldn't you have God on your team? He is the most powerful being in the MCU so why wouldn't I take him first round.