(For Windows software, obviously.)
There used to be a lot of these around years ago. You would get a trial or shareware software title from its original source, find the crack/patch/keygen/serial that goes with it, do the needful, and use it to its full potential.
But all the crack/patch/keygen/serial search engines I knew seem to have shut down. Are any of them left? Where do people get cracks/patches/keygens/serials these days?
I only know of GameCopyWorld and MegaGames for cracks.
I don’t know about a single reputable serial/keygen site unfortunately.