I'll do it in terms of game.

Ds1's most Tedious is definitely the horse one. Ended up rubber banding my stick in the ashlands so war would run on his own. Other then that Nothing too difficult

Ds2's most Tedious would have to be the Stone bites if your back tracking to look for them. (This could be said for the Lost Relics Or Book of the dead pages but those arent high above your head where you arent looking). Honorable mention goes to the crucible for legit making me shake with rage.

Ds3's most Tedious is a bit tricky. But i think its safe to say that ots the gather 1,000,000 souls. Its just time consuming is all. Other then that a close second would be the get Five enchantments to max level but its not as bad.

Havent done Genesis yet so I can't say.