Guild Wars 2

Has this happened to anyone else?

My group killed the Hybrid and noone died at all through the whole instance. However, I didn’t get the achieve for killing the Hybrid or Killing him without dying.

Had you already finished the pre-requisite: Tower Antitoxin Injector?

You must kill the Hybrid and then inject the antitoxin before the other two achievements (Tower Hybrid Master [no dying] and Tower Hybrid Slayer [just killing him]) are unlocked.