Frost is already pretty amazing. Out of my 1500 hours, about 45% of that time I've been playing frost. He's honestly pretty tanky. Up his armor and sit in your bubble if you feel threatened.

But... his 1 is pretty much trash. His 1 should just be ice wave.

Make his 2 his bubble, it should work the same, but charge the button to explode the bubble, dealing the remaining bubbles health as damage to any enemies in it or "x" range around it.

Give him a 3 that deals no damage, but freezes everything in "x" range for "x" duration. Maybe it could even increase his armor too?

Keep avalanche as is, keep the freeze, blind and all that but maybe buff its damage and various durations? He kind of doesn't need buffs on avalanche though but some damage increase would be nice as it currently falls off hardcore at high levels.

But most importantly, change his passive to grant additional damage to Frozen targets. Make it so Frost is rewarded for freezing things? Kind of like the armor reduction on avalanche, but just a flat % damage increase for the Frosts damage, separate from avalanches armor reduction.

That's just my ideas, not like DE would ever use them, and frost is in a pretty decent place. I think itd be cool for him to get rewarded for freezing shit.