Honestly out of all the execution methods, firing squad is the best.
Electric chair has proven track record of failing to execute people, some times requiring multiple attempts to fully finish someone off.
Lethal injection sounds good, but due to medical organizations boycotting a lot of the materials required for prison lethal injection it’s a subpar ineffective method. Unlike the lethal injection given to animals at a vet, it causes extreme pain, the catch being that it paralyzes you before you get a chance to scream, which makes it appear to be painless.