Leveling 1 stat only?

I keep seeing videos about that but I have never tried it. I'm doing an rl1 run now, so it seems very similar. But i'm curious about it.

Have any of you tried it? What did you think?

If you were going to try it, what stat would you pick?

I think i'm leaning to either Int. or End. Both seem different but fun, but I want to hear your thoughts :)