Even as Unstoppable Jason can struggle against all of these characters:
-Gunslinger
-Imposter/Bone Shaper
-Stunt Double/A-List
-Hish-Qu-Ten
-Acidic/Tarkaten/(Konjurer?)
-Cutthroat
-Swarm Queen
-Shirai Ryu
-Piercing/Ravenous/Ethereal
-Demolition
-Dragon's Fire/Flame Fist
-Brawler/Hollywood
-Mystic
I could list more but the trend here is all of these characters can zone/control space really well, coupled with really good up close pressure of their own. Give Jason a projectile in Slasher? You take away his armor break. Give him armor break? You take away his projectile. And in Relentless Jason does have a teleport to get in but its suuuper unsafe and you also don't have that armor break OR projecticle. He can reverse controls but that's also super unsafe unless he spends the bar to make it safer. Once Jason gets in, yes, he's very strong. But trying to get in with no form of teleports or a means of counterzoning to some degree is a whole other ball park and takes much patience, practice, and reads.