dishonourably — (British) alternative spelling of dishonorably.
malevolently — wishing evil or harm to another or others; showing ill will; ill-disposed; malicious: His failures made him malevolent toward those who were successful.
perfidiously — deliberately faithless; treacherous; deceitful: a perfidious lover.
roguishly — pertaining to, characteristic of, or acting like a rogue; knavish or rascally.
traitorous — having the character of a traitor; treacherous; perfidious.