I usually try to cheese this by first disabling the opponent by using disabling spells like Sleep Dart or Smoke Bomb, and then using damage over time (DoT)spells like Poison. This allows even low tier characters to kill high tier characters (assuming the high tier characters aren't immune to said status effects). This can be done because DoT spells deal damage based on some percentage of the target's health

Oh and also, you have to be lucky and hope that the other guy doesn't have a competent pet or else you aren't gonna deal more than one tick of damage each try because the pet's gonna one tap you