。
She despised him.
Literal
She [topic-は] him [object-を] despised.
軽蔑する is a する-verb meaning 'to despise, scorn, look down on' — built from 軽 ('light') + 蔑 ('scorn'), literally 'to consider lightly.' Stronger and more condemnatory than just 嫌う ('dislike'); implies a moral judgement that the person is contemptible. Like other する-verbs that take a human object, the object is marked with を.