This isn't even a real fight.
Homelander would get his ass ROYALLY kicked by Thanos alone, even without his armies to fall back on.
Then; to add insult to injury, Thanos would snap his fingers and wipe a humiliated Homelander out of existence.
- Homelander is not a fighter. He's a super powered bully who isn't used to fighting because he's usually the most powerful being in the world.
- As evidenced in episode 6 of season 3; when fighting Soldier Boy, Butcher and Hughie or similarly powered beings, he's almost completely out of his element.
- Homelander does not adapt well to fighting against new unforseen powers or adversaries. Thanos is a warlord, a conqueror and a destroyer of worlds who would totally own him in a relatively short time frame.
'Nuff said...