>>16461848Mono-Grass, despite being my favorite type, is an absolutely terrible Monotype to run.
If you must, Cradily is neutral to both its STABs, has enough bulk to take a hit a +2 and counter back (or take at least 2 non-boosted hits), and can KO back with Rock Slide/Stone Edge. Solid counter.
>252+ Atk Life Orb Talonflame Brave Bird vs. 252 HP / 200+ Def Cradily: 156-185 (41.4 - 49.2%) -- guaranteed 3HKOMono-Bug gets Shuckle and Crustle, who both are able to take a hit. Crustle in particular can KO back, while cannot be 2HKOed unless not running Defensive EVs, at which point Talonflame still needs a 2HKO. Both are solid counters, dunno what Shuckle can do aside Power Split and switch.
>252+ Atk Life Orb Talonflame Brave Bird vs. 252 HP / 0 Def Shuckle: 99-117 (40.5 - 47.9%) -- guaranteed 3HKO>252+ Atk Life Orb Talonflame Brave Bird vs. 252 HP / 90+ Def Crustle: 142-169 (41.2 - 49.1%) -- guaranteed 3HKOMono-Fight will get Terrakion once Pokebank opens up. Mega-Lucario with full Speed investment can generally outrun Adamant Talonflames that don't run full Speed before they hit with Flare Blitz, but it's very dependent on natures and Speed EV investment on both parties. Both are checks (shaky at that).
>252+ Atk Life Orb Talonflame Brave Bird vs. 0 HP / 0 Def Terrakion: 222-263 (68.7 - 81.4%) -- guaranteed 2HKO>252+ Atk Life Orb Talonflame Brave Bird vs. 0 HP / 0 Def Mega Lucario: 227-269 (80.7 - 95.7%) -- guaranteed 2HKOSurprise surprise, Talonflame's best counter in a mono-type is the same thing as it is with any other team: Rock types.