Should capital punishment be legal?

Capital punishment is a very big deal in many countries in the world. Some countries are strictly against it, while others have it legalised. What is true is that in every country, there is a great discussion on wheather it should be legalised or not, as there are many pros and cons around this subject, and through this essay, these reasons are going to be described, both against and in favour of capital punishment.
To begin with, capital punishment is a way of getting a sort of retribution, as the criminal receives what he or she did (in case of it being a murder). Secondly, it's for sure that the threat of future crimes commited by the same outlaw is discarded. And lastly, the fact that people are aware that, by commiting that crime, they will be punished with death, will work as a deterrent effect, in other words, it would be like a warning and prevent anyone from breaking the law.
On the other hand, it can be said that capital punishment can be quite immoral, as there are many other ways in which a criminal can pay for what they did and therefore, learn the consequences. In addition, the crime would be punished with the same action, which doesn't make sense at all. And lastly, it is a very agressive way of explaining to people not to commit a crime.
As a conclusion, I think that, although it is a tough way of showing the consequences, capital punishment is a good solution for reducing crime, but only if it is completely certain that the criminal is guilty, because is the condemned is wrongfully convicted, there's no coming back. An example for this can be seen in the movie "The life of David Gale". I'm in favour because, even though it may happen once or more than once, someone that commits a crime is still a dangerous person, what means that it is a threat for the society, and as a solution, eliminating the threat would make the society safer and less afraid, as well as a society better acquaintanced with the way in which the commiting of crimes must be paid.