Assume a scenario where both players are at ten life. If Player A activates Villainous Pact on their turn and Player B attacks resulting in ten combat damage being dealt to Player A, what happens next? Does Player A lose when their life total reaches zero or does Vicious Struggle still deal ten damage resulting in both players reaching zero life?
Until your next turn, deal your opponent 1 damage for each damage you take that doesn't come from Vicious Struggle.
As soon as your opponent’s life reaches zero, the game ends and you win!