Djinn Illuminatus and Giggling Skitterspike on the battlefield.
Steps
Cast Slaughter Pact, choosing to pay its replicate cost an arbitrarily large number of times, by paying a total of ({0} magic symbol) , targeting Giggling Skitterspike.
Giggling Skitterspike and Slaughter Pact's replicate ability trigger.
Resolve the Giggling Skitterspike trigger, dealing damage equal to its power to each opponent.
Resolve the Slaughter Pact trigger, copying it for each time its replicate cost was paid, with each copy targeting Giggling Skitterspike.
Giggling Skitterspike triggers for each Slaughter Pact copy made.
Resolve a Giggling Skitterspike trigger, dealing damage equal to its power to each opponent.
Repeat step 6 for each remaining trigger.
Notes
This combo will result in you losing the game during your next upkeep step, due to all the delayed triggers from Slaughter Pact and the Slaughter Pact copies. It is highly recommended to only use this combo if you have high certainty it will end the game.