go at (someone)

1. To physically attack someone with great ferocity or hostility. Watch out for that bull in the back field—he'll go at you if you get too close. John went at the burglar with a knife to defend his family.

2. To criticize, berate, or verbally harass someone at length and/or with great intensity. At the international summit, the foreign ambassador went at the president, demanding an explanation for the recent espionage allegations.