By that, I specifically mean, "what anime makes you anything but comfortable, but rewatch anyway?" It could be for various reasons, I imagine.

In my case, two of my three regularly-rewatched anime, I do so because of the catharsis (Violet Evergarden and Your Lie in April). The third is equal parts comfort and anti-comfort, so they cancel out (A Place Further Than The Universe). All are intense enough for me to only rewatch once a year.