I would assume that the OP ban on RaHoWa and FATAL is also going to include dreck like MYFAROG, ACKS, LotFP, NuStar Frontiers, etc.
I'll get too honorable mentions out of the way first; the first of which is Numenera, which I wanted to love so much. My problem with the game isn't that it's bad, necessarily. It's not. It's just dull as dishwater. And it's just not quite modular enough to work out any character concepts that the game didn't come up with itself. Cypher has some good ideas in it, and I've even seen it done well (my daughter loves No Thank You, Evil!) but it's just... very not good.
Second is Dungeon World, which should have been an mix of PbtA and classic D&D and instead was a mix of classic D&D and PbtA. I know it has its fans so I can't call it a bad game either, but boy was it ever not at all the thing I was looking for when I first found it. I can recognize that's on me though.
The crown jewel of bad games for me though is FATE Accelerated. I have my problems with FATE Core; it's incredibly crunchy for a game that purports to be so fiction forward, so I thought dialing back on that crunch would be the solution. To that, I say, hahahahahahahahahahahahaha, oh dear lord no. Players choosing what to roll by performing the mental gymnastics of "but I do it <insert adverb here>!" every damn action got old so fast. Blades in the Dark neatly solved the problem of players choosing what skill/stat to roll off of by giving the GM more leeway on the position and effect. FATE Accelerated never even brings up the possibility. It remains the worst game I've ever run.