The last episode, Rufus is holding our Sibuna gang hostage. At some point, he drags Nina with him. What happens next? Fabian charges straight at Rufus, knocking him to the floor and allowing them to escape.
The second season finale had a few:
Jerome, held captive by Rufus, manages to crack Rufus' safe and recover the Frobisher gem.
Shortly afterwards, he takes advantage of Rufus' distraction, tackling him and manages to escape.
Eddie awakening to his power as the Osirian and using Senkhara's crown to banish her from Nina's body.
Rufus putting on the mask, getting possessed by Senkhara, and getting dragged down to Egyptian Hell. Have fun down there, you son of a bitch.
A smaller example: While being chased by Rufus, Alfie tries to close a secret entrance to buy him time. And while unintentional on his part, he closed the door on Rufus's arm. It's very satisfying to hear him scream in pain.
Victor encouraging Nina to give up the mask to Rufus, knowing fully well what will happen when Rufus puts it on.
Rufus: Listen to the old man, Nina." Victor: Yes Nina. You listen to this old man.
The third season finale:
Alfie fearlessly standing up to Fabian who's possessed, saying there's nothing he can do, and secretly video-taping the proof needed to convince KT about him.
Eddie gets quite worked up, allowing Team Evil to shove him into the Sinner's sarcophagi... only for nothing to happen. Eddie then comes out with a smug look on his face and mocks their efforts. "You really thought I was angry" indeed.
For the villains: you know that staff that would destroy Team Evil's efforts, and Eddie plants in the nick of time? Turns out they actually needed it for the ritual, and they played our heroes the entire time.
KT standing up to Patricia- when Patricia threw juice at her, KT threw cereal back. Cue Patricia left standing with a surprised look on her face as Eddie and KT leave the room.
Any time FabianTakes A Level In Badass. Tackling Rufus, standing up to Nina, calling out Joy, and nearly attacking Eddie. Sure, the latter was over a huge misunderstanding, but still, just seeing Fabian take charge and fight back definitely counts.
Another for Fabian, when he single-handedly beat Isis House in dodgeball, after spending most of the episode being forced to play the mascot.
Jasper standing up to The Collector and yanking down his hood; They turn out to be Rufus. And the best part? He gets away with it.
Joy winning the Senet Game, when seasoned players like Victor couldn't. Also when she calls out Fabian on being an Extreme Doormat.
Jerome, Fabian, Amber and Trudy are all trapped in a barn. Cue Alfie in a Big Damn Heroes moment, breaking them out...by ramming into the door with a tractor.
Amber gets a few.
Despite being blackmailed, tricking Victor with a fake bracelet, sabotaging his chances at completing the ceremony. And, in the same episode, getting Sibuna back together just before she leaves.
Sure, sometimes it gets a bit harsh, but it was always sweet to see her calling out Joy over what she does to Nina.
Being the only one of the Sibuna Power Trio to complete the hopscotch task without messing up.
Patricia also gets a few.
Walking through the tunnels and over the chasm...while blind.
Trying to be mature and telling Eddie he could date KT if he wanted to. Just, the way she finally stops letting jealousy control her, even though she's clearly heartbroken about what she's saying. Doubles as a CMOH.
In season 1, demanding answers from Mrs. Andrews, blackmailing her to make sure it happens. After half a season of secrets and hiding from the teachers, it was pretty sweet. Also, from the same episode, her snarking at Rufus- while he's got her held hostage.