I don’t really have a least favorite distribution. I mean, I guess between Fedora, Ubuntu, Debian, Mint, openSUSE, Manjaro, and Gentoo, the least appealing choices to me are Manjaro and Gentoo. Manjaro is just Arch but worse, because the packages are old and likely to cause incompatibilities with AUR packages that need really up-to-date system packages, and I…don’t trust the maintainers to have configured everything better than I could have myself. Just based on history.
Debian has ancient packages. That’s the only reason. I’d just end up using Flatpak packages or compiling from source.
Any other distribution I could use, including Gentoo, but Arch is the sweet spot for me.