Is there a single more frustrating thing then having a 4hour battle with the BBEG, just for him to make some snide remarks once you got him to a quarter of his HP and then him snapping his fingers to teleport to safety?
Feels like our GM didn't want to give up that character and by having him just escape like that, it feels like there was no way to prevent it. Even if we had dished out more damage, the NPC would have just left sooner.
We spent the past 2 months of game sessions tracking down that arse, gathering additional troops for the surprise attack on his stronghold, infiltrated it, surprised him literally in his sleep with our troops mopping up his henchmen, dropped a powerful spell on his ass to shake him awake . . . and then, when we finally got him in a corner, he just pops out of existence with his laughter echoing in the chamber. Feels like we wasted all that time and like we didn't achieve anything of substance, cause the few mooks that we did end up killing are insignificant.
We didn't stop or hinder the BBEG's plans, we didn't free someone from his terror, we didn't get him, we didn't take away anything important to him. We just gave him a rude wake-up-call and then watched him leave once the tide of the fight turned.
Defeating that guy is tied to a quest giver that we'll leave behind when we continue onwards, so next time we inevitably come across that BBEG's wrongdoings, I'll make the case that we shouldn't waste our time and resources on him again - after all, we're not even getting paid for it and I couldn't give less of a shit about whatever it is this guy is doing.
Maybe I am a bit salty over the cheap getaway, but my character is sort of on a timer and can't afford further delays for something he has to take care of quickly, so it is appropriate for him to go "fuck this shit".