I would have put this as 'best Mafia Catcher' or 'Rising Star', but both of those are more attuned to play over the course of the year rather than in a specific game. If someone with more experience of their play would like to 'nom them for those, feel free to count this towards that nomination.
In Steven Universe Mafia, it was looking as thought town was ruined. They were losing an average of three PRs per day. Reasonably Rational came into the game full force, consistently pressuring mafia player after player. I have never seen an IC play with this much resolute force and put in this much work.
The most stellar moment, however, which I will never forget, was when they completely turned the game around on Scum (who were recovering from having two of their stronger members lynched and headed towards a victory). On page 157, RR makes this post, where he details a scum slip that he's found and sussed out. It is evident in their own private chat that RR had figured all this out earlier and was slowly getting scum to slip even more and reveal as much as they would. This marked a turning point for the game, where based on this play alone, Reasonably Rational set up for an easy town win. It was only due to town misplaying heavily while scum lurked it out/played tactfully that this win was squandered, but this sort of upset was one that drove the game from being done midway in to lasting all the way to MYLO.