Let's start with the overlooked: a robot that can time travel and has access to a fourth dimension filled with a bunch of advanced gadgets can become a danger to the earth.
Some of Doraemon's gadgets can be downright scary at times. For instance, the Dictator Switch allows its user to make anyone of their choice disappear. And not just out of sight, that person is gone and no one will ever remember that person even existed... yes, even the person's own mother. And in the chapter this gadget debuted in, Nobita wound up making EVERYBODY disappear. Granted, the device is used to punish dictators and the effects are reversible but the fact that this device is sold to the public, it is very chilling.
Then there's the Devil's Passport. What does it do? Well, it lets you get away with anything... and we mean anything. Granted, in the story, Nobita felt guilty after for what he had done when he used it but... remember that in the future, the gadgets are sold to the public which includes the Devil Passport... you make the connection. How many people killed, raped, and stole, and didn't get punished?
As a bit of added Fridge Horror, keep in mind that Doraemon bought all of his gadgets himself. It's probably not worth dwelling on how he intended to use some of them.
According to Word of God, Doraemon rents two-thirds of his gadgets.
In one episode of the 2005 anime, Nobita ends up using a gadget on Shizuka's bath water that makes it freeze in place. If Shizuka had dived underwater and stayed like that for just a bit longer, she would have been trapped underwater, frozen and unable to breath.
Long-time fans may sometimes be left asking why Doraemon didn't use his other gadgets to get himself/Nobita/others out of their predicament. Though it has been noted that most if not all of Doraemon's gadgets are second-rate and thus need a lot of repairs. It's just that the repair time "tends" to be during their adventure.
When Doraemon lost his ears, he cried so hard that the paint washed off, making him blue. Okay, if Doraemon didn't want to be blue in the first place, why didn't they just paint him yellow again?