Note that Nexus's RE4 page is shared between the 2023 remake and the UHD port of the 2005 original — the most-downloaded entries here target the UHD/Steam build. Check compatibility against the version you own. For the UHD port, re4_tweaks and the HD Project are the two foundations every setup needs.
Ranked by hand, not auto-generated. Every mod links to its full page with install guide + compatibility.