title_body: What language uses the most amount of phonemes?
upvoted_answer: You're gonna have a hard time with "majority of the entire IPA". Non-pulmonic consonants are rare, and some consonants are hard to contrast (e.g. /β/ vs. /v/), while vowels are often highly allophonic. Natural languages tend to have fewer IPA places and distinction via aspiration, labialization, etc.  
  
  My best answer to your question would be Ithkuil (constructed, almost unspeakable language). It has 58 phonemes, with unusually many vowels (13). This allows it to have mostly single phonemes for morphemes. Ithkuil's Roman transliteration is a bit strange, as some phonemes use diacritics and others have digraphs, but it also has its own script (morpho-phonemic with alphabetic characters).