As far as characters in the Marvel lore who could defeat The Mad Titan Thanos by themselves single-handedly if they ever fought him, my list would be:
1- Sentry
2- Jean Grey/Phoenix (X-Men) especially if she taps into her Phoenix form
3- Bruce Banner/Hulk
4- Drax The Destroyer
5- Norrin Radd/Silver Surfer
6- Death (Lady Death herself)
7- Beyonder
8- Legion
9- Beyonder
10- Galactus
1- Sentry
2- Jean Grey/Phoenix (X-Men) especially if she taps into her Phoenix form
3- Bruce Banner/Hulk
4- Drax The Destroyer
5- Norrin Radd/Silver Surfer
6- Death (Lady Death herself)
7- Beyonder
8- Legion
9- Beyonder
10- Galactus