Isn't the whole point of being the best character loyalist only playing that one character and never using other characters in tournaments? Cowboy can have the title as the best Shinnok / Sinestro whatever player, but he isn't the best loyalist in the NRS scene. That title rightfully belongs to Jupiter.
@SaltShaker I remember Cowboy using Sonya in tournaments for MK9, so scratch off his resume as pure character loyalist title in that game. Injustice 1 I'll give him since I don't remember him using any other character aside from Sinestro in tourney. MKX he started off playing Sub-Zero for months when Shinnok was already out and then a year into MKX was using Leatherface.
Jupiter has only ever played as MMH in Injustice tournaments. Jupiter has only ever played as Jax in MKX tournaments. He's gotten consistent top eights in both games using nothing but his one respective character in both games, and has also majors under his belt.
Pretty sure Jupiter didn't go to any tournaments until a couple months into Injustice when MMH came out. Maybe Injustice 2 will be the first ever NRS game Jupiter decides to use more than one different character in tournament. That would be hype.