If its adaptive its probably fine. If the amount of the charge is higher than what the phone officially supports and its not adaptive the chance that you will damage your phone is certainly there.
Damaging the battery isn't the worst issue that can happen, worst case scenario the whole phone will die with a wrong charger.
The same logic applies to other devices of course.
With chargers, always go for an official charger or a charger of a reputable high-quality brand. I highly recommend to not cut corners with those things to save a few pennies because it might be one expensive joke.