This is a simple but effective killcounter for Stellaris.
Ships: all ships you have lost or killed in any form of combat (versus other ships, starbases, guardians..)
Pops: all pops you have killed via bombardment, colossus attacks (cracker, neutron sweep..), purge or planetary invasions
Worlds: all worlds you have destroyed with a colossus
Empires: when you kill an entire empire via war or similar (doesnt work for all things)
It tracks ALL the things above + the kills/losses of other empires.