A győztesnek nagy előnye van.

Because Hungarian often expresses have with a possession pattern:

valakinek valamije van
literally: to someone, something-of-theirs is

So:

• a győztesnek = to the winner
• natural English = the winner has

The ending -nak/-nek is the dative ending. Here it is -nek because of vowel harmony: győztes has front vowels, so it takes the front-vowel form -nek.

Because the thing being possessed also gets a possessive ending in Hungarian.

• előny = advantage
• előnye = his/her/its advantage

In this sentence, the possessor is a győztes (the winner), so Hungarian marks the noun as possessed:

• a győztes előnye = the winner’s advantage

This is very normal in Hungarian: even if the possessor is named explicitly, the possessed noun still carries a possessive suffix.

In ordinary Hungarian, possession is usually expressed with van (is) rather than a direct equivalent of English have.

So:

• A győztesnek nagy előnye van.
• literally: To the winner, a great advantage is.
• naturally: The winner has a great advantage.

This is one of the most important structural differences between English and Hungarian.

In this kind of possession sentence, Hungarian often leaves out egy when it is simply stating that someone has a certain feature, quality, part, or advantage.

So nagy előnye van is perfectly natural.

If you say:

• A győztesnek egy nagy előnye van

that is also possible, but it sounds more like:

• The winner has one big advantage
• or there is a particular big advantage that the winner has

Without egy, the sentence sounds more general and idiomatic.

This is a natural, neutral Hungarian word order.

• A győztesnek is the topic: what the sentence is about
• nagy előnye van is what is being said about that topic

Hungarian word order is strongly connected to emphasis and information structure, not just grammar.

For example:

• A győztesnek nagy előnye van. = neutral
• Nagy előnye van a győztesnek. = stronger emphasis on the advantage
• A győztesnek VAN nagy előnye. = contrastive emphasis, like the winner really does have a big advantage

So the original sentence is the most straightforward version.

Literally, nagy means big or large, but with abstract nouns like előny it usually means something like:

• great
• considerable
• major

So nagy előny is best understood as a big/great advantage, not a physically large one.

Here it is a noun, meaning winner.

It comes from the verb győz, which means to win / to defeat.

Depending on context, győztes can also behave like an adjective:

• a győztes csapat = the winning team

But in this sentence, a győztesnek clearly means to the winner, so it is functioning as a noun.

Because that is how Hungarian possession normally works in this structure.

Hungarian often marks possession in two places:

1. on the possessor
   
   • a győztesnek = to the winner
2. on the possessed noun
   
   • előnye = his/her/its advantage

So the whole pattern is not redundant from a Hungarian point of view; it is just the standard way to show who has what.

A useful model is:

• A lánynak könyve van. = The girl has a book.
• A győztesnek nagy előnye van. = The winner has a great advantage.

Yes, depending on context, that is a very natural English rendering.

The Hungarian sentence literally talks about the winner having an advantage, but in English you might translate it as:

• The winner has a great advantage.
• The winner is at a great advantage.
• The winner has a major edge.

So the exact English wording can vary, even though the Hungarian structure stays the same.