The phrase "to twist the knife" means to deliberately make a difficult situation worse for someone, by saying or doing something hurtful or cruel when they are already feeling bad. It is like adding insult to injury. Full definition
11:14 - Murdoch twists the knife into Myler, saying that if he knew of wider spread criminality «he should have told me». (politics.co.uk)
Psions are always available and always happy to twist the knife when it comes to needing some extra health to fight actual enemies. (nonfictiongaming.com)
For days, Sky News had a «Labour woes» strap on the screen as the party's opinion poll lead shrank and its grandees kept on twisting the knife. (totalpolitics.com)