The Competitive Megacombo

Any Magic player with an interest in recreational mathematics has probably heard of the megacombo; the challenge of creating a deck that can deal the most damage on turn 1. The megacombo record has long since gone off into the clouds of recursive Turing machines and numbers inexpressible in notation that doesn't risk getting you kicked off a plane. So I'd like to propose a more down-to-Earth version: the Competitive megacombo.Not originally my idea, credit to Elaine Cao. The rules are as follows:

A deck is only legal if it has top-8ed a Competitive REL tournament.If someone enters an 8-person RCQ with a deck designed to blow the previous record out of the water, I reserve the right to disqualify it. The purpose of the Competitive REL restriction is that the decks must not be tuned for dealing lots of damage all at once, so it'd be boring as soon as someone tries to game it.
The exact deck can be anything that would be legal to present for game 2 of the match. (i.e. it can include sideboard cards, and it can be over the minimum deck size.)
Any deck that is capable of dealing arbitrarily high amounts of damage is disqualified.
The deck's score is the total amount of damage it dealt to its opponent.
Unlike the old megacombo, it doesn't have to be dealt on turn 1, nor all at the same time.
You control the outcome of all random processes in your deck, and who goes first.
The opponent is assumed to have infinite life and do nothing other than draw a card every turn and discard a card to hand size. They take no mulligans, and their deck is the minimum size allowed by the format. If it matters what cards they have in their deck, it's assumed to be whatever card is most inconvenient to you. If the opponent must make a choice, they make whatever choice is worst for you.

I like this version of the challenge because it involves numbers that are much easier for laypeople to understand, it makes you do a fun scavenger hunt among all decks that have ever done well in a tournament (MTGtop8's search function is great for this), and it rewards creative use of cards that you'd never consider using in the original megacombo. It also serves a practical purpose: providing a minimum number of life you'd need to gain with an infinite combo in order to be safe from any noninfinite shenanigans your opponent could pull off.

I've divided the scoreboard by formatCounting any deck that was ever legal in that format., and I plan to keep this page updated as new records are found. To submit a new record or inform me that an existing record is invalid, contact me via any of the methods listed on the homepage. For brainstorming and discussion about this challenge, join the technical Magic discord server.

Primary records:Numbers are approximate where nobody has yet bothered to calculate them exactly.

Standard: ~2↑↑↑10
Pioneer: No record submitted yet
Historic: No record submitted yet
Modern: No record submitted yet
Pauper: ~5000
Legacy: ~10⁸⁰
Vintage: No record submitted yet
Duel Commander: No record submitted yet
Limited: No record submitted yet

Block records:Standard formats are named by the most recent set to have released.

Streets of New Capenna Standard: ~10^10²⁴
Rivals of Ixalan Standard: ~5,900,000,000
Midnight Hunt Standard: ~21,000,000,000
Phyrexia: All Will Be One Standard: ~2↑↑↑10

Pauper

Record held by Isaac King.

Deck: Jund

Get as many creatures onto the battlefield as possible. Sprout Swarm gives us 4 creatures per turn, which combined with the other creatures is around 140 by the final turn. (The final turn has to happen while we still have 16 cards left in the library.) Each creature does 1 damage on its own in the final attack, plus 4 from Clockwork Swarmkeeper. On the final turn, start with 7 cards in hand, draw 1 for turn, cast 4 Deadly Dispute, sacrifice Blood Fountain to return 2 creature cards from your graveyard to your hand, sacrifice 3 Chromatic Star and 2 Ichor Wellspring, cast Emergency Weld to return Ichor Wellspring, cast it and sacrifice it again. Play Rites of Initiation, discarding 19 cards. Final damage is approximately 24 * [num creatures]. Attacks in the intervening turns get us about another 2000 damage.

Legacy

Record held by Elaine Cao and Isaac King.

Deck: Orzhov Planeswalker Humility

Play Liliana and ult it as soon as possible. On that turn, play your next Liliana, etc. For the 4th Liliana, don't kill it, and instead keep ulting it as many times as you can. This gives about 260 emblem triggers before you have to attack on the final turn. Final damage is a little over 2^{[num emblem triggers]}.

Streets of New Capenna Standard

Record held by Iijil, with assistance from Isaac King.

Deck: Naya Aggro

We attack with a large number of creatures on the final turn of the game, triggering 4 Rabble Rousings. Most of the damage is dealt by Devilish Valet. They'll each have 8 power before the attack (put them on the battlefield with Turntimber Symbiosis), so the final damage is 16 * 2^{[num attackers] * 4} + [some negligible amount being dealt by the other creatures]. So the goal is to maximize the number of creatures we can attack with on the final turn.

The main way to do this is by creating Treasures that we sacrifice to Stimulus Package. The Gala Greeters get us 8 Treasures per turn (4 on ours and 4 on the opponent's), and the Black Market Tycoons give us 2. Every attack with Esika's Chariot makes a copy of Black Market Tycoon. All creatures attack each turn, multiplying the total number of creatures by 4 each turn.

Rivals of Ixalan Standard

Record held by Isaac King.

Deck: Pummler

All the energy cards except the Longtusk Cubs, 3 Servants, and 1 Aether Hub get you a total of 63 energy. (Greenbelt Rampager must be first.) Use the Hadana's Climbs and Cartouche of Knowledges to make an Electrostatic Pummeler a 9/9. Play all 23 lands except 1 Aether Hub. On the attack turn, cast 1 Blossoming Defense, and spend 63 energy for 21 doublings. Greenbelt Rampager lets you turn mana into energy at a 1-for-1 rate, up to a limit of 2 energy. Use 21 mana to play the Longtusk Cubs and Servants each with 1 extra mana, for 7 more doublings. Aether Hub and the last 2 mana are 1 more doubling.

Final power is 11 * 2²⁹.

Midnight Hunt Standard

Record held by u/Corrective_Brutality and Isaac King.

Deck: Selesnya Control

Make lots of Scute Swarms. The deck contains 27 lands, so that's 22 doublings. There's time to ult Wrenn and Seven twice, returning 4 Evolving Wilds each time, for another 8 doublings. Felidar Retreat effectively makes each Scute Swarm have 10 power. Final damage is 2 * 10 * 2³⁰.

Phyrexia: All Will Be One Standard

Record held by liopoil.

Deck: Orzhov Aggro

Alternate Ratadrabiks and Mondraks, then recur Mondrak 10 times with Takenuma and Gix's Command. Math is hard, I'm just gonna call it 2↑↑↑10. What's a few billion orders of magnitude between friends.