Anyone have few tips on how to KO one? They could also carry Roar, Toxic, Stealth Rock, Sand Storm, Rest and other moves along with Endeavor. It's just that it recovers full HP after using Endeavor and then there's usually Sandstorm in affect and your pokemon faints after that.
Lvl 5. Donphan is legally* the best user of F.E.A.R. Lvl 1. Cleffa is immune to hazards, so it's sash won't break. Lvl 1. Tailow isn't walled by ghosts. Lvl 2. Togekiss gets ExtremeSpeed.
Donphan's legality comes in question due to the fact that the lowest level he can be "caught" is 25, and Phanpy doesn't evolve until then. Getting a Lvl 5 Donphan requires using the Pomeg glitch, which no one's confirmed to be allowed in wi-fi or Dream World tier yet.
That said, any Lvl 1-4 Donphan is flat out illegal.
I think the most reliable counter which still has other uses would be a ghost type, preferably one with Will-O-Whisp to remove Sturdy in case there's any other surprises. Abomosnow is also great because none of the Sturdy pokemon resist hail. I don't know how popular multi-hit moves are now that they've received a bit of a buff, but those who use them commonly like Skill Link Cloyster and Technician Breloom can beat it because the secondary hit breaks the sturdy/sash. Shadow Tag Shandera is by far the best counter because it traps them and is immune to endeavor, plus it's less situational and already pretty common on
For counters which require less preparations in advance, you can send in a pokemon with low enough hp from earlier in the battle so that the shell bell doesn't fully refill health. It's a bit harder to do, but considering it only restores 1/8 of the damage done it's not impossible. There's also just using priority moves if there's no sandstorm/hail set up on the second turn to KO it first, while you can use moves with a negative priority (Dragon tail and counter come to mind) to hurt them AFTER they attack you with full health, causing them to not be able to get free health and continue the cycle.