The one that kills me is the PC release of Project Diva. Denuvo usually gets pulled after a year or so, because it's not a one-time purchase for the publisher, they charge a recurring license fee. But for some ungodly reason, SEGA's decided to keep paying to have it in a rhythm game. For two and a half years, you just... sometimes lose inputs or miss a note you should've hit, because Denuvo decided you're gonna stutter just there.
In every case, Denuvo balloons the exe file size by 4-5x (we're talking 400-500 MB for a <100 MB game exe), can increase loading times between 10-400%, and in most cases, lowers framerates between 10-40%, and can introduce microstutters. There are a few outliers where Denuvo's removal coincides with worse framerates for some reason. But essentially, removing Denuvo speeds things up a lot, especially download size and loading times.
Denuvo is a cache defeat mechanism. Of course it kills performance. If CPUs still worked like 386s and 68000s, having eight copies of every function and bouncing merrily between them would make no difference. But modern processors are only fast because they spend negligible time waiting for RAM to get its act together. Every squandered microsecond is a thousand cycles burned.