I've been playing Tribunal for the past few months and I've used it to hit week 1 Infinite every month. It's basically a guaranteed Infinite as long as you know how to identify bots. Because Tribunal always has low power on the earlier turns, the bots will always Snap and you can collect your free 8 cubes. Decklist at the end.
TL;DR: Abuse bots with Tribunal and get easy cubes. Against human players, retreat liberally since you only need a 25% win rate to eventually reach Infinite.
Deck
Metas change, but Tribunal is forever. It's kind of like how Shuri Sauron used to be ol' reliable, before the power creep kicked in. To give an idea how just how steady this deck is, I've only changed it once over the past few months, which was when Zabu got nerfed (swapped it out for Sera). The Shang-Chi nerf at the end of last year made classic Tribunal playable, followed by the Omega Red buff in February really put the deck together. If Tribunal stops working due to the numbers not being good enough, I'd be very concerned with the state of the game.
Right now, with the Patriot meta, running Tribunal might be a bit dangerous since Enchantress is back, but that's nothing our Cosmo can't handle. Always use protection.
I see that the Negative version of Tribunal is running around a lot, but I don't find it as strong. It's great to hide the last turn play, but in my opinion is not consistent enough. Negative may have a higher ceiling, but you are just as likely to miss Iron Man and Mystique and zap down Onslaught and TLT. You also lose Iron Lad, which could come in clutch on Turn 7.
As mentioned in the TL;DR, the strength in the deck is winning 8 cubes from bots. Because we don't put out much power turns 1-4, it's very easy to be losing two lanes, which will lead to the bot snapping on turn 5. You can easily snap back if you have the combo and generally, even if you don't have Magik, you can win games just off of a Iron + Tribunal stack without Onslaught.

How To Play + Notes

Standard line is Magik turn 3 or 4, and then Iron Man turn 5, Onslaught turn 6, and Tribunal turn 7 all in the same lane. The three cards in the same lane gives you 22 power across all three lanes if Magik is in another lane, otherwise it's 24 if you have all three in the same lane. As a result, you absolutely need to make sure you have enough turns to play your combo. If you can't, just hit that retreat button. There are ways around it which I give some examples below, but it's all about managing your energy to set up your combo. Without any shenanigans, you usually average around 28-30 power per lane which will win against most decks.
If you fail to draw Iron Man before turn 5, Sera turn 5, Onslaught turn 6 on the same lane can let you play out Iron Man + Tribunal turn 7.
Ravonna on T2 lets you play Jubilee on T3 and sets up a T4 Iron Man, so you can follow up with a T5 Mystique as a substitute for Onslaught in case you don't find Magik so you can T6 Tribunal.
Cosmo, though, is the secret sauce to the deck. We are obviously weak to cards like Enchantress and cards that can zap Limbo out. While Cosmo will lose you a few games because you are locked out of Jubilee or Iron Lad, it will win you more cubes overall because you won't have to worry about a surprise tech card that loses you 8 cubes. You can always Iron Lad or Jubilee Tribunal on the last turn in a separate lane if it's still in your deck too.
Cosmo will also hose some decks too like Destroy or Wong, so you can pick up those free wins with it.
Super-Skrull is important for the mirror and also helps against all of the Ongoing decks. If I'm up against an ongoing deck, the right play is Super-Skrull + Mystique Turn 7 in separate lanes, one of which has Onslaught on it. Super-Skrull however does make you weak to Loki, though if you see Loki, you best bet is the retreat. Same with if you think it's stolen by Cable. However, just remember that if you have Iron-Man + Onslaught out, their Skrull will not double the Iron-Man effect, so it can still be winnable.
Omega Red is an interesting card and might take some practice because timing matters for Omega Red. If you are winning the lane Omega is played in when you drop Tribunal, it becomes much more harder to disrupt because the boost Omega gives you will also be applied to that lane. I usually like to play Omega Red not on my Iron Man + Onslaught stack because the +3 power can be multiplied through that stack while not taking up a spot on that location. You can play Omega on the stack if you'd don't other cards to fill the stack, but I like to think of it as a fifth card on the stack than have it take up space.
As for cards to watch out for, anything that changes locations is bad. Retreat if you are up against Thanos and they have reality stone. Snowguard Hawk and Legion are even more dangerous, because Cosmo will not be able to stop these unless timed precisely.
Enchantress, Rogue, and Red Guardian are all dangerous. Cosmo protects against these though.
Magneto could hose you if it plugs up your Iron Man lane before you play Onslaught.
Locations don't matter too much since we start our game plan after turn 3. I like to spread out my early plays just in case. If you ever see Mojoworld, make sure it's filled. If your opponent doesn't fill it for whatever reason, you win just by playing Tribunal. Locations that give cards additional power should be played on. Magik away any restrictive locations.
As for substitutions, you can always swap out Skrull for another tech card, especially if you are afraid of it being used against you. Everything else I think has a role in the deck.
Overall, I find this deck to be very solid for climbing. Give it a try; it's basically Solitaire imo. Happy to answer any questions on piloting the deck.
Decklist:

(2) Ravonna Renslayer

(3) Mystique

(3) Magik

(3) Cosmo

(4) Jubilee

(4) Super-Skrull

(4) Omega Red

(4) Iron Lad

(5) Iron Man

(5) Sera

(6) Onslaught

(6) The Living Tribunal

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