I am not good at this game, and it's been a long time since I played. Just getting that out of the way first.
I arrange my six-man squad to ambush an ADVENT pod. I had lost my first skulljack and lost more than a week building the replacement, and was determined to get a hold of this pod's officer and snag whatever information Tygan was so hopped up about.
The ambush went off without a hitch, the officer wounded while his comrades died, and my first skulljacking was a complete success. Some sort of crazy hologram creature showed up, but I vaguely remembered that being a thing when skulljacking and wasn't unduly worried. I had plate armor, I had mag weapons, it wouldn't be much of an issue.
And that was when some sort of monster came barreling out of a neighboring building. A monster with 3 armor and three massive health bars. It was an absolute beast in close combat and it got an action for every one of my own. It was the Berserker Queen and although I didn't know it at the time, I was totally screwed.
The codex's first action was to create some sort of swirly thing centered on my squad. More than half my soldiers had their weapons instantly disabled, unable to fire until they could reload. I had one of the dudes outside of the vortex chuck a grenade at the berserker, trying to shred some armor, but that just pissed it off and she used her resulting reaction turn to smash him flat. I have another dude reload, and she runs for my knot of disabled soldiers. I try to have one flee, and she knocks two more of them down. They aren't dead, merely unconscious, but I already know I'm in deep trouble.
The enemy's turn comes around and the swirly thing explodes, killing the two unconscious soldiers and sending a third into a panic. He runs around, shoots the berserker for piddling damage, then gets critkilled by the codex. That's three men dead, one out for the mission, and two guys left in close quarters with an unstoppable beast, with the evac point clear on the other side of the map past I-don't-even-know-how-many as yet unseen pods of foes.
That was the point I ragequit. I couldn't stomach seeing my last good squad, carrying the last of my expendable gear, get wiped out by such a combo.