Is saying
My heart pounded as I clicked the “build application” button, not realizing that I had created my most illegal software yet...
a grammatically correct sentence? I'm having doubts about the "my most illegal" part.
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My heart pounded as I clicked the “build application” button, not realizing that I had created my most illegal software yet...
a grammatically correct sentence? I'm having doubts about the "my most illegal" part.
Illegal is not usually associated with shades of insidiousness. It would be better to provide degrees to the effects of the illicitness:
My heart pounded, ... I had created my most dangerous illegal software yet...
"My most illegal software yet" sounds odd to me for a different reason that others have not mentioned yet.
Among native speakers, the noun "software" is most commonly used as a non-count noun: it is not normally put into plural forms (like "softwares") or preceded by the singular indefinite article "a" ("a software").
For some reason, the "my most [adjective] [noun] yet" structure feels to me like it requires a count noun. Another example of this: "I gave him my best advice yet" also sounds funny to me (although "I gave him my best advice", without the "yet", seems fine).
A way to make "software" indisputably count is to change it to "piece of software". To me, this makes the sentence sound better:
I had created my most illegal piece of software yet...
An example sentence with similar structure from Appvertising - How Apps Are Changing The World, by Stephen Molloy - 2013:
Embarrassing, appalling, illogical, incomplete, erroneous — these words are rarely used to describe Apple's products but all and more have been applied to Apple Maps in what observers are calling Apple's least usable piece of software yet.
I don't actually think "(the) most illegal" necessarily sounds wrong. Here is an example that sounds natural to me in the title of a Quora question: What was the most illegal thing you have ever done on a computer?
This would be grammatical if by "most illegal" you mean "breaks the most laws". That is the most likely sense of illegal which would allow for a superlative. It's more common to think of legal/illegal as lacking degrees (per se); e.g. murder is not more illegal than stealing.
It is grammatically correct, and you might find it in informal English. It is not conceptually correct, however. Formally, legal/illegal is a binary relationship, so you would not be "more" or "less" illegal.