How is "can" used here? What does it mean?

Does stabbing one's back have the same meaning as betraying someone? If so, could you give me some examples?

Yes! You're right. "Stabbing one's back" has the same meaning as betraying someone. This is used when you trusted someone, and then they do something to break that trust or go against you. Ex: I told Terri the plans to launch my new product, but she stabbed me in the back and stole my idea. Ex: I thought you were on my side! But you stabbed me in the back to get what you wanted. Ex: You want me to tell you what I'm doing, so you can turn around and stab me in the back later? Ex: I'm scared to trust you because I've been stabbed in the back before.

Is there a specific word that indicates people who hate others?

Perhaps a casual term for someone who hates others is a "hater" or "haters," especially in reference to famous people. A more formal word is "misanthrope," but this is hardly ever used! Ex: Taylor Swift's haters hate when she has a good time. Ex: Don't be such a hater. Ex: He was a misanthrope.

What type of man is "yes-man"? Then, is there also "no-man"?

A "yes-man" is an informal term for someone who always agrees with their superior, usually their boss, no matter what. The term "yes-man" has a negative connotation because a "yes-man" is seen as weak for not being able to say no and formulate their own opinions. A "yes-man" can be a man or woman. Technically, a "no-man" exists, and is the opposite of a yes man (meaning they always say "no"), but the term "no-man" is not common. Ex: Our boss only hired her because she is a "yes-man".

How is "can" used here? What does it mean?

"Can" here shows permission which means someone is allowed to do something. Ex: You can go.

What's the difference between "holocausto" and "massacre"?

These two words are similar in meaning. A "holocaust" is a mass murder or slaughter of many people. It also can mean a very large destruction using heat or fire. A "massacre" is the act of killing many people. Ex: The Holocaust was one of the greatest tragedies in history. Ex: The Boston massacre was the tipping point for the colonies' rebellion.