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You really need to provide more context...
If it is really someone's name, you should write Javad Gavi
If it is nickname for a "lat-e mahal", for example, Javad the Cow is what we would say in English...like Ivan the Terrible

"Cow" brings silliness to my mind (like in 'silly cow', an insult). I believe "Buffalo" would be more familiar to English ears, considering the famous "Buffalo Bill". It has been used to refer to a criminal in "The silence of the lambs" movie.

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Note added at 1 hr (2023-02-26 19:25:26 GMT)
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The title should be "Buffalo Javad"

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Note added at 2 days 24 mins (2023-02-28 18:34:48 GMT)
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Javad the Cow, as suggested by the asker, is more like
جواد گاوه
which is structurally similar to
محمد خره، علی گوسفنده
not
جواد گاوی
which is more similar in structure to
جنون گاوی



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Note added at 2 days 12 hrs (2023-03-01 07:09:54 GMT)
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Some American mobsters' nicknames are 'Cadillac Frank,' 'Ice Pick Willie,' and "Joe Bananas". You will find more here

https://www.npr.org/2018/06/26/623268051/cadillac-frank-ice-...

However, it needs context, particularly how the person in question got that nickname.