diabolical
di-a-bol-i-cal
adjective
Extremely bad, evil, or unpleasant, often in a way that seems devilish.
"The team's performance was absolutely diabolical."
Thesaurus
Synonyms: demonic, hellish, infernal, diabolic, unholy, evil, fiendish, satanic, mephistophelian, devilish, mephistophelean