Mono-White Aggro floods the board with small creatures and token generators like Battle Screech and Novice Inspector's Clues, so Arms of Hadar's -2/-2 to all their creatures is an efficient one-sided sweeper that kills their 1-toughness tokens, small creatures like Lunarch Veteran, and 2-toughness creatures like Thraben Inspector. Steel Sabotage can bounce their Clue tokens from Thraben Inspector and Novice Inspector before they cash in for card advantage. Cut Abandon Attachments and Spell Pierce since Spell Pierce's tax is irrelevant against a deck full of one-mana plays, and this matchup rewards a proactive sweeper over card selection.