A Whumper with a newfound interest in histamines and allergies. They play with histamines like paint and scratch whatever they want into Whumpee, the graffiti swelling, burning, itching. Oh gods it was so itchy.
Consider as well! A Whumpee with a severe allergy. Whumper who tests how long it takes before they nearly die before administering epinephrine.
A hilarious turn of events being that the exposure accidentally starts to have an opposite effect and Whumper notices that the recorded times are improving and they're actually improving Whumpee's life. Well, that means they have more time to torture them. Just not as fun as trying to beat the clock before their throat swells.
Whumpee tries to stay positive, as swollen and sweaty as they are and is just excited that they get to eat peanut butter cups as torture this time around, scalpels and whips be damned.