Might as well post this as nobody else has put one up yet… (not sure about the IVs though, is 12/12/12 the worst you can get for a legendary shadow or is the floor still 10/10/10?).
Either way - it would be 93% if purified but can’t be bothered to spend 20,000 dust on an Articuno…
Nearly 550 Grunt Battles and still have not sighted a Shadow Lapras
I didn’t expect my luck to turn on that, either. Maybe the next grunt that taunts you that winning is for winners will be the one.
For whatever it’s worth - my first go at this team used what the game recommended, leading off with my maxed-out 98-IV Rayquaza, which got dispatched with just 3 frost breaths from this Lapras (without even getting off a third fast attack of its own). I had better success with a maxed-out 92-IV Machamp.