It's been done to death in HP fics where Harry or someone states that you can use any spell lethaly. So heres a thread where you list a few harmless spells and how they could be deadly.
Example:
Example:
chuckg said:
Anti-Cheating Charm: Since it doesn't say what kinds of exams it can be used for, define the exam as a breath-holding contest. Breathing without formally withdrawing from the exam first is cheating. "Forget" to tell target that exam is being held at all, much less procedure for formally withdrawing.
Alohamora: Focused to open the target's heart valves all simultaneously and keep them that way. Target dies of massive heart failure.
Bubblehead Charm: Hit the target with a smoke bomb from Weasley's Wizarding Wheezes, then use a bubblehead on them to keep the fumes from dissipating. Target dies of smoke inhalation.
Point Me Charm: Put the 'Point Me' on a lawn dart, then launch your new guided missile into their head. For extra lethality, use poison tip.
Reparo: Start with one small plastic garbage bag. Coat inside with glue. Then shred bag until its barely a plastic necklace, with tattered scraps hanging off of the neck of the bag. Slip "necklace" over target's head and quickly cast reparo charm, leaving target stuck with intact plastic garbage bag glued over their head.
Alohamora: Focused to open the target's heart valves all simultaneously and keep them that way. Target dies of massive heart failure.
Bubblehead Charm: Hit the target with a smoke bomb from Weasley's Wizarding Wheezes, then use a bubblehead on them to keep the fumes from dissipating. Target dies of smoke inhalation.
Point Me Charm: Put the 'Point Me' on a lawn dart, then launch your new guided missile into their head. For extra lethality, use poison tip.
Reparo: Start with one small plastic garbage bag. Coat inside with glue. Then shred bag until its barely a plastic necklace, with tattered scraps hanging off of the neck of the bag. Slip "necklace" over target's head and quickly cast reparo charm, leaving target stuck with intact plastic garbage bag glued over their head.