Fishing - for every other skill we have kinda power technic to skill it up even for taming and ninjitsu, so if you prepared enough it will not be so painful.
But fishing is taking eternity even with veteran fish rod, fish is weight to much so you have to throw it out or feed cat constantly and if you don't have rod you will need goat and gains are so slow...
Don't get me wrong fishing itself is fun and HIgh Sea fishing content is very very fun for me atleast, but it is worst and boring skill to train.
The ones where i can't find 70 points in sots for.
Veterinary - it is a major grind fest. It is the one skill that I buy a Mythical Token for to avoid grinding the skill.
Taming. by far the most boring skill from 50-90 (still boring at 90-120 )
Taming. My second character many years ago. I think it took me nearly a year to get to GM, then going on quickly with unicorns to Legendary. I wouldn't do it again. Evenso, great memories taming ridgebacks on the way in Savage Village.
my top 3 in no particular order: taming, imbuing, poisoning...painful!
Taming, Provoke and Discord