Hi NeronSparda!
I assume you are new to Construct? You should read some beginners tutorials, and keep the manual in your bookmarks, it really helps to solve most of basic problems.
Your problem is about picking the right instance of an object. An instance is pick when it fills a condition. From what you described, your event should look like this :
Player - On collision with Enemy
Player - Animation "punch" is playing
-> Enemy destroyed.