Mono-Blue Stiflenought wins by casting Phyrexian Dreadnought and using Stifle to counter its 'sacrifice creatures' trigger, leaving a 12/12 trampler in play on turn one or two; your red blasts are the critical interaction here, because countering their Stifle lets the Dreadnought's trigger resolve and forces them to sacrifice it. Beyond stopping the combo, Red Elemental Blast and Pyroblast fight through Counterspell, Foil, and Daze to push your burn and creatures through, so hold them up as mana permission rather than spending them speculatively. Apply maximum pressure with your one-drops and Call of the Herd—their deck is light on early interaction, and forcing them to use counterspells on creatures leaves their combo unprotected. Be wary of Powder Keg sweeping your board; develop two to three threats rather than flooding, and don't extend Grim Lavamancer and Mogg Fanatic into the same Keg activation if you can avoid it. Naturalize has almost no mainboard targets, Seal of Fire deals irrelevant damage against a creatureless deck, and Rancor is too slow and fragile against a heavy counter suite.