Not everyone is running a 6/5 legendary as their leader that can kill in a few hits
Alternatively, you could go the spell route and include cards like Relentless Assault, Final Fortune,Last Chance and Warriors Oath to guarantee yet another round of combat to close out a game but that seems like another deck entirely
Imp's Mischief is your black card for this effect, with the slight drawback that you lose life equal to the spells target
This could make an excellent card for a blue deck focused on tempo
I 1-dropped it when a foe had a Silklash Spider, a nasty 2/7 that can control the game in multiplayer
2 Thrasios, Triton Hero Sink All That Mana Commander 2016 brought with it a ton of incredibly powerful legendary creatures with the Partner ability, which lets you have two commanders so long as they both have partner