Nidhogg 2

Self Sacrifice

Kill yourself with your own arrow

Comeback Kid

Get eaten by the nidhogg after nearly allowing your opponent to do the same

Bloodlust

100 total kills in one match

Memories

Trap your opponent on your sword for a long time while moving it up and down

Trapped in Donkeyspace

Play a match lasting longer than 20 minutes

Flesh and Blood

Beat the singleplayer game

Domination

Win the faceoff and never lose the arrow in a singleplayer match

Slow Played

Let the timer run out in your opponent's last screen and win in sudden death

Algorithms

Beat the singleplayer in under 20 minutes

GTD

Finish an 8 player tournament

Old School

Play a match with old school settings

Hogglike

Dominate every level in one singleplayer game

Valkyrie

Win 100 ranked games through matchmaking