Progress bars going to 100%. Many games are guilty of this, Baldur's Gate 3 most recently. If 100% are loaded, why am I seeing the loading screen still? The game should be starting. You're clearly not at 100% if I'm still watching the loading screen. It should be impossible to see a fully filled progress bar.
Artificially make progress bars stop at 99% if you must, it's still better than watching 100% being a clear lie.
Progress bars are bad indicators for representing remaining work or time, but it's a decent indicator that something is still being done. Though it's uncommon these days, I remember several instances of older games that has stopped loading. Showing the same percent for a minute is a decent indicator that something has gone wrong.
While I don't care for percent as a displayed number, I do enjoy some kind of indicator showing that the loading is progressing.