Mọi người đến, trừ tôi.

Mọi người means everyone or everybody.

• mọi = every
• người = person / people

Together, mọi người is a very common way to say everyone in Vietnamese.

In this sentence, it refers to all the relevant people in the situation. Because the sentence then says trừ tôi (except me), the idea is everyone else came.

This is the normal Vietnamese word order:

• Mọi người = subject
• đến = verb

So it follows a basic Subject + Verb pattern:

• Mọi người đến = Everyone came / Everyone arrives

Vietnamese often uses a straightforward word order like English, although it does not mark tense the same way English does.

Đến usually means to come, to arrive, or to reach.

In this sentence, it means came or arrived, depending on context.

Examples:

• Tôi đến rồi. = I arrived already.
• Khi nào anh đến? = When are you coming?

So Mọi người đến means everyone came/arrived.

Vietnamese verbs do not change form for tense the way English verbs do.

So đến can mean:

• come
• comes
• came
• will come

The exact time is usually understood from:

• context
• time words
• aspect markers such as đã, đang, sẽ

For example:

• Mọi người đã đến, trừ tôi. = Everyone had already come, except me.
• Ngày mai mọi người đến, trừ tôi. = Tomorrow everyone is coming, except me.

In your sentence, the tense is understood from the surrounding context.

Trừ means except, excluding, or minus, depending on context.

In this sentence, it means except:

• trừ tôi = except me

You may also see trừ in math:

• Năm trừ hai bằng ba. = Five minus two equals three.

So here, trừ is being used in the except/excluding sense, not the math sense.

Here, trừ functions like a preposition meaning except or excluding.

So:

• Mọi người đến, trừ tôi. means
• Everyone came, except me.

You do not need another verb after trừ in this sentence. Trừ tôi is just an exception phrase attached to the main clause.

Vietnamese pronouns do not change form the way English pronouns do.

In English:

• I and me are different

In Vietnamese:

• tôi stays tôi

So:

• Tôi đến. = I come / I came
• trừ tôi = except me

That is completely normal. Vietnamese does not have separate subject and object forms like English does in this case.

Yes. Tôi is just one possible pronoun. It is a neutral and fairly standard way to say I.

Depending on who is speaking and to whom, Vietnamese could use:

• mình
• tớ
• em
• anh
• chị
• con
• and others

For example:

• Mọi người đến, trừ em. = Everyone came except me.
  (if the speaker refers to themself as em)
• Mọi người đến, trừ tớ. = Everyone came except me.
  (more casual/friendly)

So tôi is not the only option; it depends on relationship and situation.

The comma separates the main statement from the exception phrase.

• Mọi người đến = main clause
• trừ tôi = exception

The comma makes the sentence easier to read and gives a slight pause, similar to English:

• Everyone came, except me.

In informal writing, some people might omit the comma, but keeping it is clear and natural.

Yes, absolutely.

Adding đều makes the meaning of all/everyone slightly more explicit:

• Mọi người đến, trừ tôi.
• Mọi người đều đến, trừ tôi.

Both are natural.
đều adds a stronger sense of all of them did.

So:

• Mọi người đều đến, trừ tôi = Everyone came, except me.

Yes. Some common alternatives are:

• Ai cũng đến, trừ tôi. = Everyone came, except me.
• Tất cả mọi người đều đến, trừ tôi. = Everybody came, except me.
• Ngoại trừ tôi, mọi người đều đến. = Except for me, everyone came.

These are all understandable, but they differ a little in tone:

• Mọi người đến, trừ tôi. = simple and natural
• Mọi người đều đến, trừ tôi. = slightly more explicit
• Ngoại trừ tôi... = a bit more formal or emphatic

By itself, mọi người can mean everyone in the group being discussed, and whether it includes the speaker depends on context.

In this sentence, the speaker is clearly excluded by trừ tôi, so the meaning is effectively:

• everyone else
• all the others

So while mọi người by itself can be broad, the phrase trừ tôi removes the speaker from that group.

It is fairly neutral.

• mọi người is common and natural
• tôi is a neutral pronoun
• trừ is standard and correct

So the whole sentence works well in normal speech and writing. It is not especially slangy, and it is not overly formal either.

If you wanted something more casual, you might change the pronoun:

• Mọi người đến, trừ tớ.

If you wanted something a bit more formal:

• Mọi người đều đến, ngoại trừ tôi.

Yes, it can.

For example:

• Trừ tôi, mọi người đến.
• Ngoại trừ tôi, mọi người đều đến.

This puts the exception first for emphasis.

Compare:

• Mọi người đến, trừ tôi. = neutral statement first
• Trừ tôi, mọi người đến. = emphasizes the exception more strongly

Both are grammatical. The original sentence is very natural and concise.