However, the better of you will be your attendant.
Interesting and Hidden Aspects:
The translation of the word "greatest" here is not one the form of the word Christ uses. Indeed, "greatest" is not a term he ever used. The word translated as "servant" is misleading because the KJV almost always translates a different Greek word as servant. Also notice, that it is not God that is served but people serving each other.
The Greek word translated as "but" joins phrases in an adversarial way. Since it always falls in the second position, translating it as "however" often captures its feeling better.
There is no Greek corresponding directly to "he that is." This is added for clariety because the following word, "greater" is introduced with an article, making it a noun not an adjective.
"Greatest" is from an adjective that is the comparative form of the word meaning "big" or "great." It means "bigger", "higher", "longer", "greater" and simply, "superior." Christ uses it more like we would use the word "better." When it is introduced by an article, it means "the better." It is not the superlative form (i.e. "greatest"). Christ never uses the superlative from because it would refer to God.
There is no "among" here. It is word is simply the possessive from of "you," which is "your" or "of you."
The verb "shall be" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition. It is in the future tense.
The "your" here is the same word as used above. Notice that these are not God's servants, but each other's. This is the most important idea in this verse because of what follows.
The word translated here as "servant," actually means "servant" or "attendant" in the sense of someone who is volunatrily employed to attend someone. It is not the Greek word usually translated as "servant," which really means "slave," someone who serves because that is the role he was born or sold into.
ὁ (article sg masc nom) "He that is" is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." Here it is separated from the noun by a conjunction.
δὲ "But" is from de which means "but" and "on the other hand." It is the particle that joins sentences in an adversarial way but can also be a weak connective ("and") and explanation of cause ("so") and a condition ("if").
μείζων (adj sg masc nom comp) "Greatest" is from meizon which means "bigger", "higher", "longer," and "greater" and is the comparative form of megas, which means "big" and "great." The superlative form "greatest" is megistos, μέγιστος.
διάκονος. (noun sg masc nom) Servants" is from the noun diakonos, which means "servant", "messenger," and "attendant." This is the source for our word "deacon." As a verb, it is from diakoneô, which "to act as a servant", "to minister," and "to perform services."