I'm only doing the MCU, since there are so-so-SO many characters and with all there powers and, it's real confusing. When it comes to how powerful is the character, we have to look at the different categories, there is many but I'll focus on these major 4. Strength, Intelligence, Speed, Battle Knowledge.
Strength: (Physical Strength) Pre-Infinity war hulk wins this, the angrier he gets, the stronger he becomes. (Magical Strength) Dr. Strange, Scarlet Witch and Jean Gray I would say tie for magical strength.
Intelligence: Bruce Banner/Post-Infinity war hulk, Tony Stark, and Dr. Strange come close but Charles Xavier Wins this category.
Durability: The Hulk again.
Speed: Quick Silver now lets move on.
Battle Knowledge: Captain America and Bucky.
Here is my list and yes I only did heroes because I'm Tired.