huchureul neomu manhi neoheossdeoni masi neomu ganghaejyeosseo.

-었더니 connects two clauses and often means something like:

• after doing X, I found that Y
• because X happened, Y was the result

So 후추를 너무 많이 넣었더니 맛이 너무 강해졌어 has the feeling of:

• I put in too much pepper, and then the taste turned out too strong
• Because I added too much pepper, the flavor became too strong

Compared with simpler connectors, -었더니 often gives a sense of the speaker noticing the result afterward.

This is about particles.

• 후추를: 를 marks the direct object of 넣다 meaning to put in / add
• 맛이: 이 marks the subject of 강해지다 meaning to become strong

So the structure is basically:

• 후추를 너무 많이 넣었더니 = after adding too much pepper
• 맛이 너무 강해졌어 = the taste became too strong

A useful way to see it:

• You add the pepper, so pepper is the object
• The taste is what changes, so taste is the subject of become strong

Because 많이 is the adverb form, and here it modifies the verb 넣었더니.

• 많다 = to be many / much
• 많이 = a lot, much, in large quantity

So:

• 너무 많이 넣다 = to put in too much

By contrast, 많은 is an adjective-like form used before nouns:

• 많은 후추 = a lot of pepper

In this sentence, we are describing how much was added, so 많이 is the correct form.

강해졌어 breaks down like this:

• 강하다 = to be strong
• 강해지다 = to become strong
• 강해졌어 = became strong

So this is not just saying the taste is strong. It says the taste became stronger / ended up strong as a result of adding too much pepper.

This -아/어지다 pattern is very common:

• 약하다 → 약해지다 = to become weak
• 크다 → 커지다 = to become big
• 조용하다 → 조용해지다 = to become quiet

Yes, literally it means the taste is strong, but in natural English it usually means:

• the flavor is too strong
• the taste is overpowering
• the seasoning is intense

It does not necessarily mean spicy.
With 후추, it means the pepper flavor is too noticeable or overpowering.

So 맛이 너무 강해졌어 sounds natural in Korean for food that became too intense in flavor.

Korean often drops subjects when they are obvious from context.

In this sentence, the person who added the pepper is probably:

• I
• or whoever is already being talked about

So Korean does not need to say 내가 unless it is important for emphasis or contrast.

For example:

• 내가 후추를 너무 많이 넣었더니...
  = When I added too much pepper...

Adding 내가 is possible, but leaving it out sounds very natural in everyday Korean.

Because it modifies two different things:

• 너무 많이 = too much
• 너무 강해졌어 = became too strong

So it is not really redundant. The sentence is saying:

1. the amount of pepper was excessive
2. as a result, the flavor became excessive too

Korean often repeats words like this more freely than English does.
You could say it with only one 너무, but using both sounds natural and clear.

In careful textbook-style Korean, 너무 often means too much / excessively, so it often has a negative result.

That is exactly how it works in this sentence:

• 너무 많이 넣었더니 = I added too much
• 너무 강해졌어 = it became too strong

In modern casual speech, 너무 is also often used like very in positive situations:

• 너무 맛있어 = It’s so delicious
• 너무 예뻐 = So pretty

But in your sentence, the meaning is clearly the original too much sense.

Yes, you can say:

• 후추를 너무 많이 넣어서 맛이 너무 강해졌어

This also means I added too much pepper, so the taste became too strong.

The difference is nuance:

• -아서/어서 = straightforward cause-and-effect
• -었더니 = after doing it, I found that this was the result

So 넣었더니 can sound a little more like:

• I added too much pepper, and it turned out that the taste became too strong

It has a slightly more experiential or discovered-result feeling.

That ending is informal, casual speech.

• 강해졌어 = casual
• 강해졌어요 = polite
• 강해졌다 = plain written / diary / narration style

So the full sentence in polite speech would be:

• 후추를 너무 많이 넣었더니 맛이 너무 강해졌어요.

The casual version is natural when speaking to friends, family, or someone younger.

A helpful breakdown is:

• 후추를 = pepper
• 너무 많이 = too much
• 넣었더니 = after putting in / because I put in
• 맛이 = the taste
• 너무 강해졌어 = became too strong

So the sentence follows a common Korean pattern:

• [cause/background] + [result]

More specifically:

• [object + quantity + verb-더니] + [subject + result]

Korean often saves the main result for the end, so the final part 강해졌어 carries the main conclusion of the sentence.