LogFAQs > #950487213

A blizzard would definitely kill it, or at least come very close.

The reason her Garchomp is so nasty is first and foremost that Garchomp itself is a beast. It's very fast and hits like a truck, but it's also reasonably sturdy.
It also runs obscenely powerful attacks: in D/P, it has Earthquake(100 BP), Dragon Rush(120 BP), Giga Impact(150 BP), and Brick Break(75 BP). Dragon Rush can miss, and Giga Impact is basically Hyper Beam(because Hyper Beam became a special attack in Gen 4). Add in the fact it likely has several levels on your team(particularly on a first attempt) and it's not hard to see why it's a challenge. Unless you have something really sturdy(that's not weak to any of its attacks), most of your pokemon are going to die in 1-2 hits.

In Platinum, it swaps out Brick Break for Flamethrower and drops 4 levels. And before you ask, yes: Garchomp is a respectable special attacker, and you're very lucky it's not Fire Blast. Brick Break comes back in rematches, and also it shoots up to level 78.