Carefully read the documentation for the End Job Abnormal (ENDJOBABN) command. Other than a forced PWRDWNSYS, I don’t know of any way to end such a job.
Ending the subsystem won’t help. The ending of a subsystem is always delayed until all jobs running in it have ended.
ENDJOBABN isn’t an especially terrible or dramatic thing to do, but you should be prepared to recognize the things that come after it. The “abnormal IPL”, for example, might cause your standard startup program to work differently. If you have PTFs that are waiting for an IPL, they will probably wait until the subsequent IPL.
Just read and be clear on the documentation. If you’re comfortable with what it describes, then go ahead with it. If not, then post back here for more discussion.