Thanos can't permenantly put either Rider down, but he might be able to discorperate them for long enough to count as a KO.
Although I don't know, as Johnny has reformed his head in seconds after having it blown apart by Possessed Jack O Lantern, and the longest he's really been KO'd for was against WWH, which was only for a few moments...
That being said, I doubt, outside of the PS, that either could do that much damage to Thanos, due to his shielding, durability etc.