my go-to compressors are:
-xfer ott (often the first thing to go on my vocals as it makes them clear and crisp, i usually adjust it a bit to tone it down some; it does not go on every instrument but it might go on some of them); another free ott-style compressor is sixth sample's cramit but i usually just use the xfer one
-presonus native compressor
-the compressor built in to izotope neutron 3 elements (which i got free in a promotion, it is a paid product generally speaking)
-tdr kotelnikov (mostly on master bus to glue everything together); molotok is another one from the same company, i don't really use that one as of now though
-la-2a emulation (i use the one by universal audio, which was free for a bit a while back, but analog obsession la-la is a known free option)
-vola, another levelling amplifier, is a free and voice-optimized levelling amplifier if it counts as a compressor
-auburn sounds lens is a pretty cool one that allows for mixing with the dry signal, it eats up pc power though
-the aforementioned analog obsession has a ton of free compressors among many other effects; it's a gold mine of free effect vsts
-kilohearts has a whole bundle of plugins with simple gui, including a compressor; i don't use this one a ton