But -- (CW) The Greek word translated as "but" denotes an exception or simple opposition. It is used to emphasize the contrast between things like we use "instead," "but instead,"or "rather." It is not the common word usually translated as "but." It is the Greek word "other" like we use "otherwise." Jesus almost always uses this conjunction to connect a negative clause, "not this," with a positive one, "instead this." However, followed by the negative used, its sense is "still" or "at least."

I -- This is from the first-person, singular form of the verb.

say  -- The word translated as "I say" is the most common word that means "to say," "to tell," and "to speak,"  but when used with an objective noun or pronoun, the sense is "say of" or "speak of."  When two accusative objects are used, the sense is  "say of him this," or "call him this." The form Jesus uses to describe his own speaking can be either indicative, "I say/tell" or subjunctive, "I should/could say/tell."  It also has many ancillary meanings such as "to count" ("to number" or like we might say, "to recount" a story) or "to choose for yourself."

 unto -- This word "to" comes from the dative case of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object.

you -- The Greek pronoun "you" here is plural and in the form of an indirect object, "to you," "for you," etc. As the object of a preposition, this form implies no movement, but in a fixed position or events occur at a specified time or while the action was being performed. With the "to be," it acts as a possessive, "yours."

which  -- (WW) The word translated as "the" is the Greek definite article, "the," which usually precedes a noun. Without a noun, it has the sense of "the one." Before an adjective, participle, or infinitive it changes the following word to act like a noun. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

hear, - -- (WF) "Hear" is from a Greek verb that means "to hear," "to hear of," and "to listen." It has the same sense as the English not only of listening but of understanding.   It also means "to listen" and "to understand," but amusingly, it also means "to be silent." The accusative object is the person/thing heard about, while the genitive is the person/thing heard from.  However, two genitives can be used with the sense of "hear of a thing from a person.This word is a participle, not an active verb.

"Love -- (CW) The word translated as "love" expresses a lot of different ideas including "to be fond of," "to greet with affection," "to persuade," and "to be contented with." Jesus however, applies it to relationships where we have a duty to care for others: family, God, etc. Another word, also translated as "love," is used to for relationships of affectionate friendship that are more voluntary. To distinguish this word, translating it as "cares for" seems to work best. See this article on love for more information.

your -- The word translated as "your" is a plural, second-person pronoun in the genitive case. This pronoun follows the noun so the possessive "of yours."

missing "the/this"  -- (MW) The untranslated word is the Greek definite article," the," which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," and "those"). See this article for more. 

enemies, - -- The word translated as "enemies" primarily means "hated," "hater,"  "hateful," and "hating." It is an adjective used as a noun. The use of this word is very specific in Greek literature. It describes one who was a friend, but who has been alienated and refuses to be reconciled. It is from a rare Greek word meaning "hate," but it is not from the Greek word that Jesus uses for hate. It is usually translated as "enemy" in the KJV.  However, from Jesus's point of view "the enemy" seems to be "hating" others.

do -- The Greek word translated as "to do" has the primary meaning of "making" or producing" something or "causing" or "performing" as service. When it means It describes a productive action.  In English, "do" is also frequently a helper verb. This Greek word is not used as broadly.

good -- The word translated as "good means "good," "beautiful," "noble," or "of good quality."    It is most often translated as "good" juxtaposed with "evil" in the New Testament, but the two ideas are closer to "wonderful" and "worthless," "noble" and "base."  See this article on the Greek words translated as "good." -- As an adverb,the word translated as "well" means, "well," "rightly,"  "happily,"  "thoroughly," "altogether," and "deservedly." 

to -- This word "to" comes from the dative case of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object. The most common is a "to" for the English indirect object. However, the translator can choose other prepositions: "with,"  "in,"   "of,"  "as," "by," "for," "at," or "on" depending on the context.

them   -- (WW) The word translated as "them" is the Greek definite article, "the," which usually precedes a noun. Without a noun, it has the sense of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

which  -- (IW) There is nothing that can be translated as "which" in the Greek source.  IW - Inserted Word -- The word "which"  doesn't exist in the source.

hate -- (WF) "Hate" is a Greek verb meaning "to hate." The word is not primarily an emotion as it is in English. Instead, it is a negative state, not being devoted to someone and not liking them. See this article on Greek concepts of love for more information. This word is a participle, not an active verb.

you, -- The "you" here is the second-person, plural pronoun in the form of an object of the action or preposition. As the object of a preposition, an accusative object indicates movement towards something or a position reached as a result of that movement.