Talonflame doesn't really invalidate any one Pokémon, but it does act as a massive constraint in the teambuilder phase. If you're building heavy offense you're going to have a very hard time dealing with CB and SD variants, whereas balanced and defensive builds have a hard time vs. BU, stallbreaker and bulky SD variants (stall moreso with stallbreaker than balance, who just faces it as a SpD psuedo-sponge/utility 'mon). Volcarona has been heavily limited by it, with it's sheer presence making a sweep impossible short of Coba Berry+HP Rock, and it's not exactly helped Pokémon like Celebi, Shaymin, Roserade etc. due to them having a hard time really touching it short of baiting it and having it catch a HP Rock as it comes in (or, in Celebi's case, U-turning/BPing on it). I think it has definitely played a major role in the viability of Rock-type coverage, with it being the sole reason that SEdge/Ancient Power is (or at least used to be) a thing on Heatran, and it is also a major part of why SEdge is the primary option for PhysDef Lando as opposed to Toxic or HP Ice or whatever else it can run in that slot. I think the sheer fact that offense often uses Lando as their Flying-type "resist" really says a lot about this 'mon, as beyond Talonflame it doesn't really make that good a Flying-type answer considering that jolly Mega Pinsir wins if it doesn't mega as it comes in (Hyper Cutter blocks drop, 100.7 - 118.8% -- guaranteed OHKO), adamant Mega Pinsir has a very good shot even if it does mega first when SR is up on Lando's side (83.2 - 98.1% -- 68.8% chance to OHKO after Stealth Rock) whereas it can't come in on Tornadus-T at all.