Niel rhymes with:
anneal, corneal, corniel, daneel, kneale, kneel, macneal, macneil, macneill, mcneal, mcneel, mcneil, mcneill, mcniel, menil, neal, neale, neall, neel, neil, neile, neill, o'neal, o'neil, o'neill, oneal, oneil, oneill
Niel sounds like:
nail, naill, nale, nall, nalley, nally, namely, neal, neala, neale, nealey, neall, nealy, neel, neeley, neely, neil, neile, neill, nel, nela, nelia, nell, nella, nelle, nelli, nellie, nelly, neola, newall, newell, newhall, newill, newley, newly, nial, niall, niemela, nil, nila, nile, nill, nilly, noel, noell, noelle, nohl, nola, nole, nolie, noll, nolla, nolley, nollie, nolo, nominal, nominally, nowell, noyola, nuala, null, nunley, nunnally, nunnelley, nunnelly