Versatile R-T

R-T is one of my favorite brawlers simply due to how versatile the character is. It can switch from long to short range engagements, deal high burst damage, corner people into unwinnable encounters and overall has a good balance between survivability and turning people into elixir slushies at the press of a button.
Of course, this isn't without any downsides. Some maps simply do not allow R-T to use their entire kit. R-T thrives in an enviroment where you can switch between poking people down and turning into Jacky but better to absolutely burst down that annoying Leon that's been stalking your thrower for the entire match.
This playstyle however fits VERY well in Duels. He has more health than the average long ranged brawler, more burst than the average melee, and can gain damage reduction when switching into his super. And since Duel maps are (most of the time) designed for both melee and ranged brawlers, R-T is constantly in their element.
Make use of your gadget to counter any pesky assassins or tanky melee brawlers trying to turn you into a pile of scrap/garbage can (Ash will get jealous).Counters:
Throwers - If you can't reach them, they sure can reach you. On maps with a lot of walls but with little distance between them throwers can make sure you are always in their range.
Maps that cater to a single brawler type - No one wants to only make use of half their kit, which is why you shouldn't.
Burst damage - As R-T, you live and die by the burst damage. You can deal it, but you are also susceptible to it on account of only having 7k base health, and people will likely target you if you can't reach them while you are in super. Unlike Jacky, you can't afford to be slightly out of range because you lack damage reflecting capabilities.