The power of the Scarlet Witch against Thanos was on display in both Infinity War and Endgame. It was also acknowledged in WandaVision - she very nearly beat him. Now, having fully embraced her power as a witch and practitioner of chaos magic, it's clear - Wanda would destroy Thanos.

Can Wanda defeat Thanos?

When the rest of the Avengers returned, Wanda Maximoff trapped Thanos using her powers and actually could've killed him, but she was stopped by a bombing raid from Thanos' ship. Although it was heavily implied Wanda could've beaten Thanos alone, WandaVision now confirms that as a fact.

Is Wanda stronger than Thanos?

7 STRONGER: THE SCARLET WITCH

Thanos is a powerful being in his own right, but he required the Infinity Stones to accomplish his goals. Without them, he may be strong, but he is nowhere near as strong as Wanda Maximoff, otherwise known as the Scarlet Witch. ... She even held off Thanos while she did it.