Shadowverse

It's much simpler and more obvious. Out of a thousand players who take the portal into unlimited mode on the last stage, statistically, there will always be a few who win due to favorable matchups and opponents who choke. As for the cards, the class has a terribly limited number of options for customization, so for the past six months, all you can do is change the third slot and swap Sapphire with Ironforged and vice versa. This depends not on the mode, but on the player's preferences (i.e., the degree of their insanity). The only truly essential addition in this pack is one or two Magnas, although I definitely wouldn't take her in unlimited mode. She doesn't counter anything, not even the Beetle, Atomi, or Daria on levels 4-5-6. She doesn't counter anything there, except for the mid-game Sword and, to a lesser extent, the Summit Priest.

Added 16 minutes later

It seems that instead of the third Sapphire, there are Ironforged units here, but damn, she's more stable.

*drumroll*
In my deck, with which I reached 10k in Master, there are two Sapphires and one Ironforged. I replaced the third Sapphire with him once just to try it out, and it turned out to be not bad. Why? Exclusively because there are now more Maryannas, who also throw out Radiants, and this is often enough, so now, in addition to winning with the board, you can also have this backup plan. This way, you can immediately sit on both the chair with Pikes and the chair with Udam, as I like. But here, I just managed to find the ideal balance for myself – discarding the Sapphire is being a loser, taking three Ironforged, as they did in CG, together or instead of Sapphires, is also a super-terrible idea. And the unit is garbage, and you clutter up the pool. But putting one 4-3 unit on the Deus effect, restoring the PP spent on it, and throwing Radiants into the pool for the pre-Sapphire late game, when you can already play them calmly, is good. If the Ironforged appears before Deus, then this is, of course, unlucky, because the unit is complete garbage. Therefore, taking more than one is like spitting in your own soup. Regarding unlimited mode, we could discuss that you don't reach level ten there, "so it makes sense," but going into unlimited mode on the portal is not a good idea in principle. What kind of suffering will you choose, does it really matter?
I often felt how much I missed the third Sapphire, but I just didn't know where to get more slots, so I sweated through tears. I even had to throw out the third Rift, but that didn't hit as hard. And all because – thanks to the Sword – I had to find two slots for Magna at all costs. Although now I already know what I would remove to get the third Sapphire back, but it's no longer necessary.