"mischievously" in the adverb sense
1. badly, mischievously, naughtily
in a disobedient or naughty way
"he behaved badly in school"
"he mischievously looked for a chance to embarrass his sister"
"behaved naughtily when they had guests and was sent to his room"
Source: WordNet® (An amazing lexical database of English)
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