Lapras is too slow to sweep. It can tank with 130 base HP and rather good defenses. Try (3rd gen):
Lapras@Leftovers
Modest Nature
EVs: 252 Special Attack, 156 HP, rest in defenses????????????????
~Thunderbolt
~Ice Beam
~Toxic
~Heal Bell(pokemon XD)/substitute/...something else
My first shot at lapras. Good water-absorber.