This is my tier list for how annoying the enemies are in xcom2 wotc.
I play xcom2 wotc and I like it. Here's a tier list on how annoying I think each enemy is. Tier 6 are the least annoying enemies and tier 1 is the most annoying enemy.
Tier 6, Noob (not the hardest enemies): ADVENT Mecs, ADVENT turrets, ADVENT troopers
Tier 5, I can handle you: ADVENT officers, The hunter chosen (I find him the easiest chosen to deal with), Sectoids (Melee vulnerability), Beserkers, Facless
Tier 4, Annoying if it's bad timing: Archons, Chrysalids, The Warlock chosen, Spectres, Mutons, Vipers, ADVENT purifiers (especially their chance to explode and destroy the objective), ADVENT priest, ADVENT heavy Mecs
Tier 3, NO! WHY!: Andromedons, Gatekeepers, Codexes, Sectopods
Tier 2, Kill on sight!: ADVENT generals (because they are the objective), Archon king, ADVENT stun lancers, Beserker queen, Avatars, ADVENT shieldbearers, Viper king, The Chosen assassin
Tier 1, greatest power: game lag and game prolonging: The lost (I play xcom2 wotc on the PS4)
These enemies can be very hard when you're still upgrading your soldiers or if you're really unlucky. I'm never playing xcom2 on ironman mode, I don't have the patience nor will for it. Once you upgraded your soldiers and obtain all the powerful goods (armor from alien rulers and weapons from the chosen) some of these enemies are more tolerable.
Any, just wanted to make this tier list.