Best Counter Lapras

For lapras I like arcanine with fire fang and fire blast

if you dodge very well:
Magneton(spark +discharge),
Kabutops(any quick move+ Stone Edge),
Omastar(Rock Throw+Rock Slide,Rock Throw no longer available and hard to dodge with that long CD )

Higher CP counters:
Arcanine,
Flareon(need some dodge),
Pliwrath(mud shot+submission)

I usually use Arcanine (Fire Fang / Fire Blast), as it is supposed to be the best Pokémon against Lapras. Omastar with Rock Slide is also pretty good. If you don't have very many elite attackers, even Vaporeon does alright. Key to beating Lapras however is dodging well.