"Master, you cannot! Thanos is the most powerful being in the universe!"
Korath on Thanos
Is base Thanos really "the most powerful being in the universe"? of MCU's most powerful beings. Let's see how far can he really go, because if you ask me, my boy Korath was never more wrong!
For a purpose of this thread, let's assume all feats Thanos performs without the direct use of an infinity stone (without powering up the gauntlet and using it's hax, specifically, like for example crushing Vision's vibranium forhead or beating up Hulk) are the feats that qualify as the feats for his base form. I know it's debatable if the stones might or might not buff his stats but let's just highball him as much as possible, to see how good can he do at his hypothetical best.
Random encounter on neutral grounds, the battlefield is indestructible. No infinity stones for all, unless a note says different. No BFR, win by death.
1. Ronan (base)
3. Ultron (vibranium coated)
6. Scarlett Witch
7. Thor (Mjolnir)
9. The Ancient One (dark dimension amp)
10. Doctor Strange
11. Hela (Asgard amp)
12. Surtur (Eternal Flame amp)
13. Odin (composite, movies + prime feats)
15. Star Lord (Celestial powers)