Using a trident enchanted with channeling, loyalty 3, unbreaking 3 and mending I couldn't get it to charge creepers with either a direct or indirect hit. The lightning animation occurred. Three throws killed. Other mobs were also affected. Creepers didn't glow, increase blast or cause other mobs to drop heads (zombie, skeleton or creeper). This was attempted on a grasslands biome at night during a thunderstorm.