Balatro

Here's what you need to do for this achievement: to get a Gold Sticker on a Joker, it must be on your team after beating the Ante 8 boss on a Gold Stake run (the hardest difficulty level). Thus, every single one of the 150 Jokers in the game (some of which are quite useless) must be present at the end of one of your wins. Also, the game doesn't seem to register this achievement right away; even after collecting all the stickers, I had to win another Gold Stake run before it triggered.

Just a warning to start with: this is a massive investment of time, and it may ruin your enjoyment of the game. Balatro is balanced around White Stake, not Gold Stake, and I really don't know why the dev forced you to play so much on Gold Stake (which is far more RNG dependent and is much less flexible on Joker configurations) for completion. It's a small blemish on an otherwise wonderful game.

With that said, there's an exploit I found which does help a fair bit with the time investment. I don't know when or if it'll be patched on Xbox (which at time of writing is still stuck at 1.0.0b, which sucks because there are numerous balance patches we're missing). I'll update this solution if it gets patched out. But, for the moment, here it is. I've confirmed that the exploit no longer works. You'll have to earn the Jokers and Gold decks the slow way now. (On the plus side, some balance changes are coming which should make Gold much less annoying.)

Here are a few more tips that will be useful, even when doing Completionist++ the "correct" way:
- Like in most roguelites, you can cheat a little by making "checkpoints" using offline save techniques. If you load a game, go offline, play a little, delete your local save, then go back online and restart the game, you'll recover back to the point you loaded. This can let you preview a seed (particularly helpful to know what Jokers and deals might be coming up), or even fish for new Jokers near the end of a run.
- I mostly used the Checkered deck, but I've heard the Plasma, Ghost, and Abandoned decks are also a lot easier to win Gold Stake runs on. YMMV.
- Cavendish is a Joker that can only spawn after Gros Michel (the banana) destroys itself. Fortunately, Gros Michel is a great early-game Joker anyway, and Cavendish is almost a run winner by itself, so just be sure to buy Gros Michel when you can.
- Madness can coexist with eternal Jokers (and still powers up). Similarly, spectral cards that destroy Jokers will still work but won't destroy your eternals. It's interesting that eternal Jokers, usually a pain, have this minor benefit too.
- The Lucky/Stone/Gold/Steel/Glass Jokers can only spawn if you have cards of that type in your deck. You should use lots of Glass (and some Steel) cards anyway, as they're great at saving runs when you can't quite hit the blind target.
- The Legendaries are a pain. It actually took me 22 Soul cards to finally collect my 5th. If (like me) you get to the end of Completionist++ and are still missing them, the way to farm them is to constantly restart, looking for the "Mega Arcana Pack" skip tag on the first two blinds. Keep doing this until one of them has a Soul card. I was able to get one every 30-60 minutes this way, but it was very boring. I believe that this has been patched, so you're now guaranteed to get a Legendary you need a Gold Sticker for. You probably won't need to farm.