Mine is the lag in Stellaris, and lack of options to let me impact it. Like let me disable the ability for the AI to make habitats FFS!
It’s Quake II, yes I’m old but they just remastered it and you should check it out. There’s a nice difficulty curve up until the last two levels, which are basically the easiest levels in the entire game. Seriously, the last boss which has been hyped up the entire game just stands in his corner shooting easy to dodge BFGs, and can be killed in about a minute, even faster if you use Quad damage.