Elite Four: Lorelei

Round one of five, with no healing in between except from your bag.

Step 1: Lead Electric

Thunderbolt from Pikachu or a Jolteon hits Dewgong, Cloyster, Slowbro and Lapras hard - four of her five.

Step 2: Handle Jynx differently

Jynx is Ice/Psychic, so Electric is only neutral. Hit it with a strong physical Normal attacker instead - it has 35 base Defense.

Step 3: Pack Ice Heals

Lapras's Blizzard was 90% accurate in Generation I with a 10% freeze chance, and frozen Pokemon never thaw on their own.

Step 4: Play around Rest

Dewgong will Rest back to full. Break through it or switch and come back while it sleeps.