わりぃ, 悪ぃ, 悪ィ, ワリぃ, ワリィ

In Japanese, warii 悪ぃ means "sorry" or "my bad" most of the time. It's also spelled 悪ィ, わりぃ, ワリィ, etc. It's a relaxed pronunciation of warui 悪い, so everything warui means warii means too.

Manga: Holy Land, ホーリーランド (Chapter 1)

Nuance

In manga, characters that used warii 悪ぃ tend to be guys, delinquents, gang members, etc. Since it's colloquial speech, it's not used by more refined characters.

To have a better idea of how the word is used creatively:

Of course, you don't need to be part of an album called "Ghetto Love" to use warii. In reality, more average-looking, non-delinquent-looking guys use it. It's just that in anime and manga the usage tends to be toward delinquent types.

Although both warui and warii can mean "sorry," it's not literally an apology, it's an admission of fault: "I did something bad." Since you're admitting you're wrong, it implies you're apologizing.

Most of the time, warui and warii have the same meaning as suman すまん and gomen ごめん, which are informal versions of sumimasen すみません or gomen nasai ごめんなさい.

But in some cases, warui and warii might sound too weak of an apology for the gravity of the situation. For example: if by accident someone ended up in the hospital, you don't say "oops, my bad." You give a proper apology

Likewise, if a character says warii in a grave situation, other characters may get mad at him for not apologizing properly.

Spelling

Although warui 悪い and warii 悪ぃ look similar they're spelled differently: the relaxed warii is has a small kana in the okurigana:

悪い (warui)
悪ぃ (warii)

To avoid confusion, authors generally write the word in katakana, or, when written with kanji, leave the small kana in katakana:

ワリィ (warii in katakana.)
ワリぃ (mixed variant.)
悪ィ (warii in kanji with small i ィ in katakana.)

Examples

Although warii often shows up in the "sorry" meaning alone. It's interchangeable with warui. For example:

atama ga warui 頭が悪い
atama ga warii 頭が悪ィ
"Head is bad."
Stupid.
un ga warui 運が悪い
un ga warii 運が悪ィ
"Luck is bad."
Unlucky.
naka ga warui 仲が悪い
naka ga warii 仲が悪ィ
"Relationship is bad."
In bad terms. Mad at each other.
kakko warui カッコ悪い
kakko warii カッコ悪ィ
"Bad-looking."
Lame.
kimochi-warui 気持ち悪い
kimochi-warii 気持ち悪ィ
"Bad-feeling."
Gross.

悪ィ

Manga: Holy Land, ホーリーランド (Chapter 1)

Context: speaker mistakes someone for someone else.
warii...
悪ィ･･･
[Sorry]...
hito-chigai!
人違い！
[Wrong] person!
- Literally "different person," as in, different from the one the speaker thought it was.

ワリぃ

Manga: Gintama 銀魂 (Chapter 9)

Context: Hijikata 土方 heard that his boss fought the main character and lost, so he went for revenge, and lost, too.
warii
Kondou-san
ワリぃ
近藤さん
[Sorry,] Kondou-san.
ore mo
makechimatta yo
俺も負けちまったよ
I also ended up losing.

ワリィワリィ

Manga: Holy Land, ホーリーランド (Chapter 6)

Context: guys leave girls behind because the plot is more important.
moo~~~~
もォ～～
(expression of frustration, see: mou もう)
- Come on!
- Really?
- Are you serious?
- etc.
bakaa!!
バカァ！！
[You] idiot!!
warii warii
ワリィワリィ
[Sorry, sorry].
mata kondo na'!
また今度なっ！
[See ya, later, 'kay!]
- kondo 今度
  Next time. (literally "this time." I'm not even joking. It means this time but means next time. This is just your friendly occasional reminder that Japanese hates you.)