unassailable             
adjective uk/ˌʌn.əˈseɪ.lə.bəl/ us/ˌʌn.əˈseɪ.lə.bəl/
 不可战胜的
in such a strong position that you cannot be defeated
  This win has given the team an unassailable lead. 结果使这支球队遥遥领先。 
 The president looked unassailable with over 60 percent of the vote. 总统以高于百分之六十的选票获得绝对优势。 
  无可辩驳的;无懈可击的
impossible to doubt or argue with
  unassailable logic 严密的逻辑 
 The conclusions were unassailable. 这些结论无懈可击。 
  固若金汤的;攻不破的
impossible to attack
  an unassailable fortress 固若金汤的要塞