How should a world where healing potions exist be treated. They have a massive benefit but could easily be used for evil.
A massive benefit, plus potential misuse, seems to be a reason to regulate them. In the real world many medical drugs require prescriptions by a physician.
But is your world organized enough to have regulations of this kind? When I read about potions, I think of fantasy adventures in a pseudo-medieval or pseudo-ancient setting. They didn't have the government agencies to verify prescriptions.
A lot would depend on the setting and potions. Do they give invincibility? Regrowing limbs? Protection against magical attacks? side effects?...etc.
Given the fact that they cause no damage to others but simply provide healing to people, I don't think so. They are not guns, knives, bows, or other means of causing damage. They can only heal. So would would people be against them in the first place?
If you are worried about crime just supply your police, or their equivalent with their own healing potions.
Reasons for regulation might include but not limited to: religious reasons, addiction reasons, causing demonic possession, undesired magical effects in general, undesired side effect as well like insanity even if temporary, political reasons, economical reasons, monopoly reason...etc.
For example imagine a conflict between a magical guild and merchants guild. The wizards have all the sick potions but the merchants want to force them into something, like cheaper prices, so they get religion/state involved and start campaigning against the product. The wizards decide to hit back and use similar means to pressure the merchants. Like using a more fundamentalist religious group to campaign against money lending or prostitution rings run by the merchants.
Similar to the above if you have a ruler who hates the supernatural you can ban healing potions. Much like alcohol/drugs/cigarettes banning of history and/or real life.
Even with strong healing magic I think, unless it's crazy stuff, guns or spears can still kill. Again it depends but if you cut the head off of a person or riddle their lung with bullet then they might not be able to heal or even have time.
Lastly. when you add magic then there should be a balance. For example a wizard can wield a lot of power. Great. So much like how a king would have bodyguards to protect from harm they would have battle mages to protect them for magical dangers. This is not exactly ground breaking. So even if the potions have a lot of cool effect, I'm sure equally potioned or magically enhanced people can still counter it. And for the little people. Well. A simple knife or club can still kill or do serious damage. No reason to deny people healing because of fear.
Well... This is a little hard just because of that little territory of real world examples that I dont know about and dont want to get into.
I understand that healing potions could be used by the right criminals but I just get the idea of healing potions being just medicine though really potent. I mean, high powered weapons and armor are one thing but I doubt if in real life we'd have a lot of controversy over healing potions. Especially when they'd be availible for military and enforcement personel and even civilian use.
The real issue I could see is the potential high cost and giving criminals an alternative to formal medical treatment but maybe people wouldn't ban a miracle drug just because the wrong people could use them the same way we dont ban painkillers and first aid kits.
I feel like in the most realistic scenario, the selling of healing potions could be regulated by the government. Like you need to be an approved alchemist to make them legally and you'd have to go through different checks and paperwork to monitor where the healing potions go from production to purchase.