I was thinking of making it look like scratched glass since their faces are behind glass. So the x and -- on Deadman's forehead fits to the aesthetic of the bots. But it may not be as visible as what you did.

Scratches would be amazing too! And scratches would make more sense since they're meant to be a scar. The digital choice was purely aesthetic because it was the one that would look more noticeable, and since his scar is so important for his design, I thought I should make it stand xD