There is no short answer to this question as it greatly depends on the context and grammar rules of the language you are using. While spell check can be a helpful tool, it is important to remember that it is not always 100% accurate.
For example, in English there are many words that are spelled correctly but used incorrectly (e.g. their/they're/there, your/you're, its/it's, etc.), and spell check will not be able to catch these errors. Additionally, there are many words that are spelled differently depending on the context (e.g. effect/affect, accept/except, etc.), so it is important to choose the correct spelling manually.
Similarly, in other languages there are often words that are spelled the same way but have different meanings (e.g. homonyms in French: faire/fer, Maine/mane, etc.), so spell check will not be able to catch these errors either.
Therefore, while spell check can be a helpful tool, it is important to remember that it is not always 100% accurate.