"We were close! We were SO CLOSE!"

Whatever object Dabi just threw after setting on fire, it's ash before it even hits the wall. His entire body burns with the irritation of unsatisfied revenge; he's been planning and planning for years. A few setbacks are expected, but for an important step like this to go awry makes him feel like he's back at square one. Like his entire revenge plot is going to go up in smoke.

He lights something else on fire and throws it. At this point, you're almost worried he might set himself ablaze, for good reason. "Every single day that bastard walks around still alive is one day too many! I want him to suffer, damn it!"

... Not good. You wonder if you should step in, or just leave him to his tantrum.