Question

agonizing
 ( also Brit   agonising)  adj   [more ~; most ~]
  : very mentally or physically painful
   a long and agonizing battle with cancer
   She made the agonizing decision to cancel the trip.
   The agonizing wait was finally over.
   He was in agonizing pain.
  ag·o·niz·ing·ly ( also Brit   ag·o·nis·ing·ly)  adv  
   an agonizingly painful condition
   They moved at an agonizingly slow pace.