Giving money is a kind gesture. Give them so much money at one time they will be crushed by the sheer weight of the money. 908,000 one dollar bills weighs 2,000 lbs, so you should be able to give a person 908,000 one dollar bills at one time and they will be safely and securely crushed to death. And then you can just take your money back right after the crushing, so this option presents no financial loss.
Compliments are kind. Compliment them so much they get an inflated sense of self and think they can do anything. If you tell someone, "Hey man, you could really fly that jet, no problem. You're an ace!" enough it will seep in and they will believe it. But they will not be able to fly the jet and they will die, though they will do so confidently and happily.
Muscle atrophy. By opening all doors for someone every time they go through a door, the person will just waste away. Their muscle mass will decline to the point where they have none, and they will die. But the will die happily knowing their good friend consistently opened the door for them, always.
Cheeseburgers. Everyone loves 'em and no one can resist 'em. That is 100% unequivocally true. Feed them cheeseburgers until they have such high cholesterol and blood pressure they have a heart attack and die. But they will also be thinking, "Man, I love these free cheeseburgers."
People love small animals, even people who are allergic, and giving a puppy or kitten is the image of kindness. Get someone who is intensely allergic to puppies ten puppies and they will die. Then you get to keep the puppies, which is being kind to yourself.
It is a very kind and caring thing to send a person a card or a package. Just keep sending cards and packages until the person gets tons of paper-cuts and the packages fill up their entire apartment. They will bleed and be squished and die. But they will do so surrounded by physical evidence that someone is thinking about them. Which is nice.
The average American watches six hours of television a day. If you give them a big ass TV they will increase that viewing time so much so that they will be unable to do anything else, and they will starve and die. But they will do so watching their favorite shows, which will be fun.
This one is pretty easy. Send the person on a vacation to either a dangerous place or to do a dangerous activity, or both. If you send someone spider hunting in the deep Australian outback there is a good chance they will die. And what is more kind than sending a person on vacation? Nothing.
Just do it! You read this whole article and clearly want to kill someone, so just do it! Push them into a canyon and they will die.
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