Наказание оказалось слишком строгим.

Наказание is in the nominative case. It is the subject of the sentence: the thing that turned out to be too strict.

It is also neuter singular, which matters because the past-tense verb agrees with it.

Here оказалось means turned out to be.

So the sentence is not just stating a fact. It suggests that this became clear later, or that the result was somewhat unexpected.

Compare:

• Наказание было слишком строгим = The punishment was too strict.
• Наказание оказалось слишком строгим = The punishment turned out to be too strict.

The second version has more of a sense of discovery or realization.

Because Russian past-tense verbs agree with the subject in gender and number.

The subject is наказание, which is:

• singular
• neuter

So the verb must also be neuter singular:

• masculine: оказался
• feminine: оказалась
• neuter: оказалось
• plural: оказались

Because оказаться already works like to turn out to be. It can directly link the subject to a description.

So Russian says:

• Наказание оказалось слишком строгим

and does not need an extra быть.

This is normal with verbs like:

• быть = to be
• стать = to become
• оказаться = to turn out to be
• казаться = to seem

Because after verbs like быть, стать, оказаться, and казаться, the noun or adjective describing the subject is often put in the instrumental case.

So:

• наказание = subject, nominative
• строгим = predicate adjective, instrumental

This is why Russian uses:

• Наказание оказалось слишком строгим

rather than a nominative adjective here.

A similar pattern:

• Он был врачом = He was a doctor
• Она стала известной = She became famous

Also, строгим is the correct instrumental singular form here.

Because of a Russian spelling rule: after г, к, х, you normally write и instead of ы.

So the instrumental ending here is written -им, not -ым:

• строгий → строгим

This is a spelling rule, even though the grammar ending is the one you would expect for this adjective form.

Yes. That sentence is correct.

The difference is mainly in nuance:

• было слишком строгим = simply states that it was too strict
• оказалось слишком строгим = emphasizes that it turned out that way, perhaps after reflection or after seeing the consequences

So both are grammatical, but оказалось adds the idea of a discovered result.

No.

• слишком = too
• очень = very

So:

• слишком строгим = too strict
  implies excess; stricter than acceptable
• очень строгим = very strict
  just strong degree, not necessarily excessive

That is an important difference.

It is from оказаться, not from оказать.

These are different verbs:

• оказать = to render, provide, show
  for example: оказать помощь = to provide help
• оказаться = to turn out, to find oneself, to prove to be

Here we need оказаться.

The ending -лось is made of:

• -ло = neuter past-tense ending
• -сь / -ся = reflexive marker

So оказалось = neuter past of оказаться.

Yes. Russian word order is flexible, and changing it changes the emphasis more than the basic meaning.

Neutral order:

• Наказание оказалось слишком строгим.

With emphasis on too strict:

• Слишком строгим оказалось наказание.

Both are correct. The first is the most neutral and natural in many contexts.

Not always. Depending on context, наказание can mean:

• punishment
• penalty
• sometimes sentence in a legal context

So the exact English translation depends on the situation. But grammatically, the sentence works the same way no matter which of those meanings fits best.

The main stresses are:

• наказа́ние
• оказа́лось
• сли́шком
• стро́гим

So you can pronounce the sentence roughly as:

• наказа́ние оказа́лось сли́шком стро́гим

Getting the stress right helps a lot with sounding natural.