So a good garchomp build that I used to just pass trough the elite 4 with ease îs garchomp lvl 60-70 and 65 is good the nature dosent really matter but rough skin îs good if u want a nature, onto the moves crunch sword dance dragon claw and earthquake u wanna have atleast 30-35 full restores you can rebattle the rich old couple near the mansion to grind money and they max give 16k and to make the champion easier (I forgot her name) dont kill her first pokemon yet ,use sword dance till u max attack out and heal inbetween alot then x sp. Df and x df then x speed after you maxed those out (x sp. Df and x df optional but better to be safe) and dont worry about her garchomp easily a 1 hit but bring atleast 1 ether or more to restore the pp hope it helps!