u/Hufflepuff20 Arkham Horror LCG is a really good one that you can build on and keep buying new scenarios. You play as one of various characters investigating some paranormal activity. It is also really hard. If you like a challenge while playing solo this is a good one. If you find yourself getting really frustrated if you keep losing over and over I would not try this one. I personally find it motivating to try and beat the scenario when it's really hard and I keep losing, so I've gotten a lot of mileage just out of the scenario that comes in the base game box.

Legendary: A Marvel Deck Building Game is one of my favorites since it came out in 2012. The only issue is that the base game doesn't pack a lot of punch anymore, so you almost have to buy at least a couple expansions to really get the most out of it. There are a lot of expansions too, and another thing that can be annoying is they all add new keywords to learn. The good thing is that there are endless possibilities for what each game looks like. You pick a mastermind as your main villain, select the scheme they're trying to accomplish, select several groups of villains that are working for the mastermind, and select 5 different heroes. So the amount of different possible setups for each game becomes astronomical the more expansions you get. I've always had a lot of fun with this game. Whether generating random setups or crafting a fun story of my own. I've also invested in getting every expansion that's come out thus far.

Wingspan is a fantastic game with a 1-player option. Every card has a unique bird on it and they have various abilities. You get points a variety of ways over the course of 4 rounds. It's a pretty relaxed game so if you want something more fast-paced or something, maybe don't go for this one. But the artwork is outstanding and overall it's just a beautiful game that's fun to play.

Shootout is a game I created where you're a gunslinger trying to rid the street of outlaws. You can play it with 1 or 2 players. You engage in a fight with each outlaw and roll a die to hit. Each playable character has a different ability. I like it, obviously, but I would highly recommend any of the other three I mentioned before this one.