Lapras is the best Suicune counter in the game, no question. It absorbs Surf, it 4x resists Ice Beam, it doesn't give a shit about being Roared , it can hit it with Thunderbolt or Phaze it out with Roar or Perish Song (Perish Song is particularly useful for the dreaded last poke CMcune). Poliwrath works well as it has Water Absorb too and can even pull off a Belly Drum on it if it's lucky and actually do some damage. Tentacruel with Haze and Toxic beats Suicune as well. That's all I can think of off the top of my head for creative counters. Oh yeah, Mantine with Haze and Toxic works decently against any non-Ice Beam variant and Psych Up Regice defecates on Suicune.
Lanturn (which you seem to object to) also stops the new breed of Suicune that you see quite a bit on the ladder - (the Offensive CM with some Speed investment, and Hydro Pump, Ice Beam, and HP Electric), but generally the best bet when countering the overgrown blue Labrador is just to force it to Rest and hit it hard with something like CB Heracross when it's asleep.
all triangular entities are liars