Well, for the average human, mittens is basically impossible to beat. Stockfish is technically stronger than mittens, however mittens style of chess is very trappy and therefore feels more punishing.
is Mittens the best bot?

I asked a couple of people about which bot is hardest to beat and most of and most of them said "Mittens is the hardest to beat" so I did some research and the hardest bot to beat and instead of Mittens I got Stockfish
Stockfish is not a bot on chess.com, it is a chess engine. A classic case of apples and oranges.

Well not knowing Mittens "actual" rating, not 1 elo and MORE powerful than a average player it's difficult tell what is the cat's rating and if it's the strongest bot. So if put a test: stockfish 12 vs Mittens. If Mittens wins then I think it's the most powerful bot

You can beat Mittens by time-out.
I'm kinda surprised someone's replying to a post i made on January 7th

I asked a couple of people about which bot is hardest to beat and most of and most of them said "Mittens is the hardest to beat" so I did some research and the hardest bot to beat and instead of Mittens I got Stockfish
Stockfish is not a bot on chess.com, it is a chess engine. A classic case of apples and oranges.
You can access stockfish from the bots menu by scrolling down to the bottom.

I wish I got to know Mittens. My cat died about a month ago. To distract myself from grief, I took up chess again after many years. I play only bots anyway, so it would have been interesting to go up against Mittens, who looks a little like Joey, my late cat. 🐱

Mittens uses a toned down stockfish.
Actually, I'm virtually certain that Mittens-bot is a version of the engine Komodo as chess.com owns the rights to using Komodo. This is what all the "chess personality" bots use I believe.
Stockfish is currently the highest rated chess engine in the world, but this means the supercomputer version and not a weaker desktop version for public analysis.
I remember when Stockfish was something like 3500, then I heard something like 3800 as technology keeps getting better and most recently Stockfish crossed the 4000 rating barrier! Okay, granted, this 4000 rating was in FischerRandom chess variant (live 960 on chess.com), but nevertheless dominant against other top engines.
I asked a couple of people about which bot is hardest to beat and most of and most of them said "Mittens is the hardest to beat" so I did some research and the hardest bot to beat and instead of Mittens I got Stockfish