Based on what other people are saying if say The moon achievement, then Grand overlord.
Then Emperor maybe it's more about everything working.
Flawless Conq deserves a mention but I got that with not much effort (doing the weekly once a week) so I believe it's more about skill and dedication also a bit of luck helps in VMA.
Xbox one EU
8 Flawless conquerors on all class specs (4 stam, 4 magicka)
Doesn't stand in red
the trophies... my main has the dwemer one (obvs) every other trophy set is missing 1 piece to complete it; i will grind the ghosts, werewolves etc etc - no drops.
get sick of it, so i go & do something else on an alt and what happens... the very trophy i was trying to get on my main drops on an alt!
Probably to convince myself that I actually need any of these achievements, is the hardest task .
PC EU (PL): 14 characters. ESO player since 06.08.2015. Farkas finest quote: "Some people don't think I'm smart. Those people get my fist. But you, I like."
I would say:
#1 The Dro´atmora (not sure how to spell it)) destroyer. Since you need a lot of achievements to get that title
#2 Flawless conqourer (probably)
#3 Emperor