Use of 悪ィ over 悪い


> それが良{い}いのか悪{わり}ィのか正{ただ}しいことなのか、少し考{かんが}える。

I interpret this clause from 僕のヒーローアカデミア as "As to whether that is a good
thing or a bad thing or something correct, I will think about it a little."

Why is 悪{わり}ィ used instead of 悪{わる}い (i.e. why the り syllable after わ rather
than the る syllable)? Also, why is the い at the end written in 小さいカタカナ rather
than ひらがな?




As you can see in @Earthliŋ's answer that I linked above, this kind of sound
change occurs quite often in colloquial speech.

> /ui/ → /ii/  
>  あつい → あちい・あちぃ・あちー  
>  わるい → わりい・わりぃ・わりー  
>  だるい → だりい・だりぃ・だりー

This is informal, and usually sounds masculine.

> why is the い at the end written in 小さいカタカナ rather than ひらがな?

Katakana often look slangy, so I think they wanted to make it look more
slangy.

Edit: As commented by @Sjiveru, the Kanatana ィ is also working as a cue for
the slang pronunciation; 悪ィ with no furigana would still probably be read as
わりい.




As you can see in @Earthliŋ's answer that I linked above, this kind of sound
change occurs quite often in colloquial speech.

> /ui/ → /ii/  
>  あつい → あちい・あちぃ・あちー  
>  わるい → わりい・わりぃ・わりー  
>  だるい → だりい・だりぃ・だりー

This is informal, and usually sounds masculine.

> why is the い at the end written in 小さいカタカナ rather than ひらがな?

Katakana often look slangy, so I think they wanted to make it look more
slangy.

Edit: As commented by @Sjiveru, the Kanatana ィ is also working as a cue for
the slang pronunciation; 悪ィ with no furigana would still probably be read as
わりい.

