At least German transliteration is 1-to-1. Slavic names among others often have multiple transliterations available. The Russian name Валерий can be rendered for example as Valery, Valeriy, or Valeri. It's very confusing for documents that require the person's name.
Also don't forget Chinese, which due to different romanizations or different dialects being used for the romanization, can result in different outputs depending on whether a person is from PRC, ROC, Macao, Hong Kong, or Singapore.
[0] https://en.wikipedia.org/wiki/Wikipedia:Romanization_of_Russ...