1. When someone does something really well.
2. When someone ruins a joke or a moment.

When someone takes something too far and just ruins the moment completely. We've all done it before, and there's always some jackass who yells out "KILLED IT" as soon as it happens.

1. When someone says or does soemthing to destroy the current flow of rich interaction.

2. When someone does something or wears something that is too sensational to describe.

Ruined something

Reference to Axe's double pits to chesty

To "kill" something you need to do it very well. After accomplishing something with great efficiency you are recommended to pump your fist to show people around you that you "killed it" also to signal people from a far distance that you killed it.

to walk into a room, looking stunning, and get the attention of everyone in the room

got a good joke or something close going and someone jus says something hella outta line and it jus kils tha joke