Spy Combo is a linear all-in combo deck that wins by casting Balustrade Spy to mill its entire library and then reanimating Lotleth Giant for massive damage or chaining Dread Return targets, so you need to counter the combo or disrupt it before it assembles. Counterspell and Dispel are your best tools — counter Balustrade Spy or Dread Return on the stack to stop the combo entirely since they have limited redundancy for their combo pieces. Envelop stops Lead the Stampede and Winding Way, the green card-selection spells that find their combo pieces, for just one mana at instant speed. Thraben Charm provides instant-speed graveyard exile to disrupt Dread Return targets and the Generous Ent / Sagu Wildling recursive elements. Fanged Flames and Skred come out as dead cards — their creatures are either 0/4 walls or one-shot combo pieces rather than creatures you need to trade with in combat.