Golovkin recently corrected his Facebook name from Gennady to Gennadiy. Lomachenko also went from Vasyl to Vasiliy. Use the correct spelling, xenophobic jerks.
Letter for letter translation: Василь Анатолійович Ломаченко Vasil Anatolijovich Lomachenko Either I or Y... I am not sure which is the correct one. From what I know it should be и=I, but I guess it varies from language to language. Regardless, the iy in Vasiliy is silent due to the ь(Василь). So his name gets pronounced differently in different languages
Vasyl is transliteration from the Ukrainian language (Василь). Vasiliy is transliteration from the Russian language (Василий). Loma can call himself whichever he likes, but in his IDs, in his bank account name (in the US), etc. it's Vasyl.
In Ukraine when you receive an international passport these ruled are unified/automated (https://www.kmu.gov.ua/ua/npas/243262567) and the Ukrainian version of your name is used for transliteration (though domestic Ukrainian passports are bilingual: Ukrainian and Russian).