Desconfío de la gente que promete demasiado y luego no cumple nada.

Because the verb desconfiar normally takes the preposition de when you say who or what you distrust.

• desconfiar de alguien/algo = to distrust someone/something

So:

• Desconfío de la gente... = I distrust people...
• Not desconfío la gente

This is just how the verb works in Spanish, so it is best learned as a unit: desconfiar de.

In Spanish, la gente is a very common collective noun. It refers to people in general, but grammatically it is singular.

That is why the verbs are singular too:

• la gente que promete
• la gente que no cumple

Even though English uses plural people, Spanish treats la gente as a singular group.

Because they refer back to la gente, and la gente is grammatically singular.

So Spanish says:

• la gente que promete demasiado
• la gente que luego no cumple nada

Even though the idea is plural in English, the grammar is singular in Spanish.

If you used a truly plural noun, then the verbs would be plural:

• Las personas que prometen demasiado y luego no cumplen nada

Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• Desconfío already means I distrust / I am distrustful
• The -o ending shows it is yo

So yo is optional here. You could say Yo desconfío..., but it would usually add emphasis or contrast.

The accent mark shows the stress and also helps distinguish the pronunciation.

Desconfío is pronounced with a break between the vowels:

• des-con-fí-o

That means the í forms its own syllable. Without the accent, Spanish spelling rules would suggest a different pronunciation.

This kind of accent is common in forms like:

• confío
• envío
• río

Here que is a relative pronoun, meaning who, that, or which depending on the English translation.

So:

• la gente que promete demasiado = the people who promise too much

It connects la gente with the description that follows.

Because here demasiado is being used as an adverb, not an adjective.

It modifies the verb promete:

• promete demasiado = promises too much

As an adverb, demasiado does not change for gender or number.

Compare:

• promete demasiado = promises too much
• demasiadas promesas = too many promises

In the second example, demasiadas is an adjective modifying a noun, so it changes form.

Yes, but the meaning changes.

• promete mucho = promises a lot
• promete demasiado = promises too much

Demasiado suggests excess: more than is reasonable, realistic, or appropriate. In this sentence, that stronger idea fits well because the person then does not deliver on anything.

Here luego means then or afterwards.

So:

• promete demasiado y luego no cumple nada
  = promises too much and then/afterwards doesn’t deliver on anything

In Spain, luego is very common in this sense. Depending on context, it can sometimes also mean later, but here it clearly means then / afterwards in a sequence of events.

Yes, but in Spanish that is normal. Spanish uses negative concord, which means multiple negative words can appear together in the same sentence.

So:

• no cumple nada = doesn’t fulfill anything / fulfills nothing

This is completely standard Spanish.

A useful rule:

• If the negative word comes after the verb, you usually also need no
  • No cumple nada
• If the negative word comes before the verb, you normally do not use no
  • Nada cumple would not work here in the same way and sounds wrong for this meaning

So no cumple nada is the correct structure.

Here cumplir means to fulfill, to keep, or to follow through on what was promised.

So no cumple nada means the person does not keep any of their promises, or does not follow through at all.

Some related examples:

• cumplir una promesa = to keep a promise
• cumplir con su palabra = to keep one’s word
• cumplir lo prometido = to do what was promised

In this sentence, cumplir is being used in a broad sense: they promise a lot, but then they deliver nothing.

Yes.

• Desconfío de las personas que prometen demasiado y luego no cumplen nada.

This version is also correct. The main difference is grammatical:

• la gente → singular verb
• las personas → plural verb

Both sound natural. La gente feels a bit more general and collective, while las personas sounds a little more explicitly individual.

Because it expresses a general attitude or habitual opinion:

• Desconfío... = I distrust / I tend to distrust

And the relative clause also describes a general type of person:

• la gente que promete demasiado y luego no cumple nada

This is not about one specific moment; it is a general truth from the speaker’s point of view.

Because the speaker is describing a type of person they see as real and identifiable: people who promise too much and then deliver nothing.

The indicative is normal when you describe something as an actual characteristic.

A subjunctive version would sound more hypothetical or less definite, and it would not be the natural choice here.

So:

• la gente que promete... = people who do promise...
• not la gente que prometa... in this context

Yes. Adding nada makes the idea stronger and more explicit.

• no cumple = doesn’t follow through / doesn’t deliver
• no cumple nada = doesn’t follow through on anything at all

So nada adds emphasis: the person delivers on nothing.

A very natural close translation would be:

• I distrust people who promise too much and then deliver nothing.

Other natural versions:

• I’m suspicious of people who promise too much and then don’t follow through at all.
• I don’t trust people who make too many promises and then keep none of them.

The Spanish sentence is compact, but the idea is exactly that: too many promises, no real follow-through.