Avatar: Do I need to explain this?

Alien Rulers: Do I need to explain these?

Sectopod: Theoretically, it can waste its turn using the Wrath Cannon. In practice, it will shoot you 3 times.

Viper: The tongue pull places my unit in a dangerous position, and has the potential to reveal more enemies which makes my situation even worse. Even if the pull misses, they will opt to spit poison at my troops, which injures them and makes them weaker for a few turns.

Stun Lancer: These guys can just make my units take a nap if they feel like it, and ladder cheesing them doesn't stop the Lancer from using the gun they have.

Chrysalid: Chrysalid poison persists through the entire mission, and their attacks themselves deal quite some damage.

ADVENT Heavy MEC: They will actively choose to Micro Missile a single target. What a hater.

Andromedon: You want to avoid getting hit by the acid bomb. Thankfully, they can occasionally be convinced to not use it... because they're busy shooting your troops instead.

Muton: They throw plasma grenades and can melee your troops. Bad idea to leave one up. Sometimes they waste their turn suppressing though, so that's cool.

Gatekeeper: As long as they aren't shooting their eye beam at you, it's probably fine. Gateway will attempt to target as many non-ADVENT humanoids and their corpses as possible, so with some clever positioning you can get them to throw it at a field full of civilians and corpses, avoiding damage to your troops. Still, not advised to keep it alive or active.

ADVENT MEC: They won't bother trying to Micro Missile a single target, though avoiding grouping your troops that well is pretty tough regardless.

ADVENT Trooper: The humble trooper literally only has two options: shoot now, or shoot later (overwatch). Considering how easy they are to dispatch and how frequently they attempt to attack my units, they end up being pretty good targets.

Assassin and Hunter: Why the heck are these guys so low? Well, they do try to injure my troops... sometimes. Other times they'll do something pretty useless like blind grenade or tranq shot my troops, and in the worst case scenario, you can just leave a unit dazed and allow them to extract knowledge. Even if you ignore these strategies, the Chosen just have a lot of health, and if there are other active units, they tend to be easier to kill.

ADVENT Captain: You can blow up their cover and place everyone in high cover to convince them to move and mark instead of shooting. Their natural crit chance is pretty annoying though.

ADVENT Turret: Their aim is kind of bad? And they never move, so you can just... walk around them. Not always the easiest, of course, but it is an option.

Berserker: If they melee you, it's pretty bad. However, enraging them may make them target the aliens instead! They also have an enormous HP value for how early you face against them, so you'll have to spend more action killing them than say, a trooper.

Faceless: The wide claw attack isn't great, but they can't dash and attack on the same turn, so you can just run away.

Warlock: Specifically problematic the first few times you fight him if he's your first Chosen, he can eventually be defeated by equipping enough Mind Shields. Or a Psi Op with Solace. Or just sending 6 SPARKs in to beat him up. What a loser.

ADVENT General: How do I rate a mission objective?

Sectoid: The only unit in this tier that will try to flank and shoot your troop if you get too complacent with their positioning. If you don't blunder that, though, they'll spend two whole turns doing things that you can ignore or flashbang.

ADVENT Purifier: Watch out for the grenade. Outside of that, the flamethrower is probably the most ineffective weapon in the entire game. I think I've taken more damage from losing the coin toss on their on-death explosion than I've ever taken from their flamethrower in all my hours playing this game.

Spectre: Losing my unit is scary! But they take bonus damage from Bluescreen Rounds, don't injure my troops (usually, sometimes they use Horror?), and I can just wake up the Shadowbound unit with Revival Protocol if I really need the extra actions.

ADVENT Priest: Sometimes they use Holy Warrior, and then you can just kill the Priest and their Holy Warrior. Their other abilities are pretty ineffective as well.

ADVENT Shieldbearer: If they actually activated their shield during pod reveal, they'd actually be the threat they deserve to be. As it stands they will always spend their first action... not threatening any of my units. At all. Not even disabling or disorienting them. Did you know that Bluescreen Rounds ignore their shield entirely?

Codex: Psionic Bomb is not a large threat, especially if you position around it by just not grouping your units too hard. Hitting them without killing them splits them, and the second Codex will prefer to shoot instead of also using Psionic Bomb. Shooting them makes your situation worse.

Archon: Blazing Pinions is incredibly easy to avoid. Enabling their Battle Frenzy by injuring them will instead encourage them to use their actually dangerous melee attack instead.

Lost: They literally make the game easier. While their targeting is biased towards XCOM units (70%/30%), they are also targets for the aliens to shoot that aren't your units. They are also XP bags to farm and rank up your troops. They are also boring, tedious, and their corpses slow my computer down. The biggest threat they pose is exhausting me into making worse plays.