Can Someone Explain This?

I'v just started being an assassin, and its quite fun having a different way to play. Me and my friend were playing each other as Assassins and we came across something weird.

We were both assassins, both had the same upgrades. Level 2 cloak and level 2 assassin.

I run up, grapple stab him in the head, he goes down to red health. As we exit the move, he grapples me, same move, and kills me?

What? Can someone explain this please ><

he has the steel peel endorsement i suggest getting it

I guess someone had a armor endorsment.

Ah, i assumed he was using a standard class. Never thought about that. Thanks, i knew the game was right and there was a reason!