Which of the following sentence choices is correct? I guess both are. But is there a difference between them?
The best way to destroy your enemy is to make him friend.
The best way to destroy your enemy is by making him friend.
1) The best way to destroy your enemy is to make him a friend.
2) The best way to destroy your enemy is by making him a friend.
The first sentence sets up a relationship between the first and second part.
The best way to do something = make x something.
The "to" is a function word that allows the two parts to relate to each other. It connects the two ideas as a general proposition. "to" can often refer to purpose or outcome of something as well.
Here is proof of this from the British Council: We use the to-infinitive: to express purpose (to answer "Why...?"): to plus an infinitive
It does not refer to how like the word by.
The second sentence with by refers to a process for doing something or how something is done.
So, by introduces the idea of how to do something.
"By making him your friend" refers to the process or activity you engage in.
Here's the proof of this from an online grammar site:
**Method— by verb-ing vs. Instrument— with (a) noun
METHOD A method of doing something can be expressed with a prepositional phrase that includes by + a gerund. (The prep. phrase is an "adjunct" to the main clause because the sentence can be considered complete without it.)**
You can open it by using a knife.