Phenax, God of Deception + Sewer Nemesis + Lord Xander, the Collector Combo

All permanents on the battlefield (Sewer Nemesis without summoning sickness and with an opponent chosen on the battlefield and Lord Xander without summoning sickness on the battlefield).

Declare Lord Xander as an attacker attacking the opponent named by Sewer Nemesis. Lord Xander's second ability triggers, causing the opponent to mill half their library, rounded up.

Activate Sewer Nemesis by tapping it, causing the opponent to mill cards equal to the cards in their graveyard, milling the remainder of their library.

Infinite mill for target opponent