a lot of characters are 'broken' in this RP already. admittedly, i have ones. like Gaster, as i'm still trying to set limits on him so he isn't able to just make all existence cease to, well, exist with a simple trigger.
Jack is meant to be a threat. but he's far from 'broken'. Andrew Hussie actually makes his characters extremely well thought out, and has made it so that Jack can be defeated, and in Homestuck, he has been killed off. other versions of himself with much different powers came in as well, but they too, were all killed off (namely Lord Jack and Robo-Jack).
Jack Noir of the Beta Session is not very creative, as stated before. he doesn't have an interest to explore the full extent of his powers, and due to going mostly insane, all he ever does is fight and kill anymore. and Jack only has one arm, as due to the prototyping, he lost his left arm. He carried his sword in his right hand, where the ring is located, making it very difficult to remove the ring, as many of the Homestuck protagonists quickly found out.
however, towards the end of Homestuck, Jack's right arm was severed in a moment of vulnerability, removing the ring, and rendering him useless. PM then killed him.
Jack is far from a broken character. Hussie is an intelligent guy when it comes to making characters, and he knows where to set limits, and how to kill off any character, even Lord English himself (though admittedly, Hussie himself was a character in Homestuck, and was killed by Lord English).