How do I prevent characters from being able to land on each others heads?

I am working on a 2D fighter and the movement seems fine, but I dont want the characters to be able to land on each others heads. I used circle colliders hoping that they would slide off, but they can still stay on top of the head. Is there something I should try in script? or Is there a way to do this with just the colliders?

Assigning a Physics Material without friction should make it so they don’t “attach” to each other due to gravity and contact.

Maybe another way to do this would be to apply a small repelling force from each object to another when they collide, so they’ll not get “stuck”.