I decided to start playing the old xcoms, and I had the most embarrassing defeat.

I just started xcom: ufo defence with the openxcom mod, and the third ufo I found was a terror ship, and with the sacrifice of one of my interceptors I brought it down(with the openxcom option that lets you start with avalanche launchers).

I landed and because I knew how difficult this came is I was careful(threw a smoke grenade in front of the skyranger and all that stuff). I managed to kill two Reapers and three Floaters and regrouped all my soldiers to enter the ufo. It was at that point I realised I had no clue where the door was, so I came up with an ingenious plan. I threw a smoke grenade by one of the walls, and I placed my soldiers at the edge of the smoke, and then I unleashed my master plan.

I armed a high explosive and I threw it at a wall of the ufo. It then exploded and wiped my entire squad. 14 soldiers to nothing in a turn. Because of my own stupidity. The worse part is it didn't even scratch the ufo.