We don't have synonyms for aggressing yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are aggressive, aggression and regressing.
(v) :
(intransitive, construed with on) To commit the first act of hostility or offense against; to begin a quarrel or controversy with someone; to make an attack against someone.
(v) :
(intransitive, construed with on) To commit the first act of hostility or offense against; to begin a quarrel or controversy with someone; to make an attack against someone.