I think that'd be a very quick fight, but thanos doesn't even have to fight Graviton in the MCU since isn't he in the Fridge.

Also If we mean comic wise, then Graviton could probably detect certain "tricks" by thanos like using the reality stone but he wouldn't really be able to do any real harm to Thanos with full infinity gauntlet.

Oh Dank you need to catch up on AOS if you think Graviton is in the Fridge.

A:EMH Graviton could totally spank any version of Thanos without any of the good stones but once he gets ahold of them things it's game over