Affinity is built around artifacts and artifact creatures, so Steel Sabotage is excellent here: it counters artifact spells like Myr Enforcer, Utrom Monitor, Refurbished Familiar, and Baleful Strix, or bounces an already-resolved artifact such as Baleful Strix or Utrom Monitor to reset their board. Note that it can't hit Thoughtcast, which is a sorcery and not an artifact. Remove Soul answers their creature spells directly, including Myr Enforcer and Refurbished Familiar. Negate is trimmed because it can't touch their creatures, which are the bulk of their threats, and Meeting of Minds is too slow against their fast curve. Sunscape Familiar's cost reduction on our blue spells and God-Pharaoh's Faithful's life gain from casting them help us keep pace while these answers handle their threats.