There are lot of remedies but there are few ways that can kill instantly.

1. Fire
Fire can kill lizards instantly regardless of the size of the lizard. If a small lizard or medium-sized lizard falls in the fire, it will be dead. This applies to a gecko, skink, garden lizard and even big lizards like monitor lizards, Komodo dragon.

2. Heavy Weight
Anything heavier compared to the size of the lizard will kill the lizard instantly. For example, it can be a heavy stone if a heavyweight falls over the lizard then the lizard will die immediately.

3. Injury At Vital Spot
Everything complex organism has a vital spot and lizard too have them. If a thing hits the vital spot with adequate force and speed then the lizard will die.

4. Hot Water
Hot water is another thing that will instantly kill a lizard, especially the small ones. Once the
lizard comes in contact with the hot water, it will be game over for the lizard.

5. Hot Oil
Much like hot water, hot oil will also kill the lizard instantly. The lizard will instantly get fried. If by any chance the lizard falls in the hot oil, then it will die immediately.