When it comes to describing someone who has "behaved badly," there are plenty of synonyms to choose from. Words like misbehaved, acted inappropriately, misconducted oneself, transgressed, and behaved unreliably all convey the idea that someone has acted unacceptably. Other options include words like acted out, behaved disgracefully, disgraced oneself, and acted rudely. Picking the right synonym can depend on the context and severity of the behavior in question, as well as the tone you want to strike when describing it. But with so many options available, you're sure to find a synonym that accurately captures the situation.