Depends which one you are talking about.
If it's blaziken considering no one knows how to use it besides the cookie cutter smogon build you can do one of two things: either kill it on the first turn with earthquake if the guy is stupid and doesnt use protect the first turn, or you can roll something resistant to fire and then use protect and watch blaz kill itself with high jump kick recoil, that or switch to a ghost type, then revenge kill with something.
If it's garchomp, its fairly easy, any fast pokemon with speed EVs that know ice punch can kill it. My electivire which is apparently not smogon approved has been killing them all day.
Dragonite is tough, luckily few people have dragonair and even less have multiscale. If it does have multiscale you are partially fucked since no one uses stealth rocks at all. If it locks itself into outrage switch to something like azumarill and scratch it a bit while it confuses itself. THats basically it when it comes to Dragonite.
Lucario is also not that bad because of the ground weakness, any fast earthquake user will one shot it. If you find that you arent fast enough to kill sweepers, than use the focus sash, the best anti sweeping item, as well as priority moves.
At a very last resort you can kill any new players with a counter/mirror coat wobuffet with focus sash.
