I'm still very not normal, by the way, about Legundo shaking Avid out of his loss-induced pyromania with "I don't need you grieving right now, Avid! I need what you know!"
Like. Recognizing that Avid was grieving. Grieving even more than we knew at the time, because Avid was also probably grieving Elle all over again (and/or for the first time, considering that Oakhurst apparently happened literally days after he killed her) along with his overarching grief and fear about turning into some kind of monster, and having lost (what he thought was) his only chance at curing himself. Bro is not in a good place.
Which Legundo sees, at least to some extent. Legs is a guy who has seen a lot apparently, in terms of people going through The Worst Possible Things and coping with it in whatever broken, flailing ways humans tend to cope. Anger, lashing out, violence, terror, weeping -- those are all things with which Dr. Legundo apparently has a lot of experience.
So for him to see Avid going at Shelby's house so violently that he set himself on fire for a moment, and to immediately process what has happened and what is going on in Avid's head... Yeah. Legundo clearly has talked people off of ledges before.
Genuinely: I can't stop thinking about the fact that Avid set himself on fire. He's wounded here. Legundo is pulling him back from the flames and probably checking to see how bad the burns are and trying to remember if he's got burn cream back in his storage and Avid is still staring at the fire with the flint hanging loose in his hand. He's weeping, you can hear it.
"I can't have you grieving right now," Legundo says -- not that grieving is bad, or that it doesn't have its place, but that we're in a war zone and grief can get us all killed. "I need what you know."
And not only does he pull Avid back from the precipice, but he immediately turns it into a distracting task. "I need what you know." Snap out of it. You are valuable to this situation, you can't hurt yourself like this, I need you to redirect and put that energy into winning this fight instead of destroying things and yourself.
...but I also like that Legundo did just kind of... stand back at first, lol. Like, let Avid get it out of his system, I guess. "This is the least healthy coping mechanism we can be using right now--" but he doesn't actually stop Avid until the house is a lost cause and there's a small threat to the rest of the village. Better the house burn than Avid do something stupid like go to the vampires and ask them to turn him too oh right sorry nevermind. >.<