this absolute monstrosity is 100k "difficulty" (which sorta measures expected time to complete one board) and I've been attempting it off and on for over a year now. there are a couple hundred people with clears of this (it probably only takes somewhere in the tens of hours for an experienced player) but this clear is mine!
even with perfect logic, I still had to guess about a dozen times and 7 of them were outright 50/50's. some consider this a flaw, but minesweeper with no guesses presents no challenge! there's a whole new game in picking the optimal guess from many possible options, and high difficulty boards take that game to an extreme.