Karma goes to heal ally being chased with her Q, but kills all 5 enemies instead.

There is a massive teamfight, your team get aced.
Enemy team decides to do baron.
They all die, and you get credit for every single one of the kills.

Twisted Fate uses Destiny in the middle of 5 enemies. Twisted Fate then uses Red Card and then Wild Cards. PENTA KILL. *Enemy team surrenders automaticly*

Kog gets whole team to low health and dies, but passive kills whole team

You are Sona and get Baron aggro on the enemy team while you're the only one on your team alive. Stun them all with ult. Kite as if your life depends on it (it does). As they're all low, your AP Ez respawns and ults them all for the epic KS penta.

Nocturne ults, then Qs a bunch of ennemies in a single line as they're fleeing for safety.

Entire enemy team dies to a single Zed's shuriken. No shadows required.

They chased Singed...

Galio ults entire enemy team into center of AP Pantheon ult.

I actually saw something like this once.

vladimir pools under 5 people and gets lucky