一徹[ittetsu] obstinate
一徹者[ittetsumono] stubborn person
貫徹[kantetsu] accomplishment
周知徹底[shuuchitettei] (something) known to all
初志貫徹[shoshikantetsu] carrying out one's original intention

徹す[toosu] to stick through
徹る[tooru] to go by
徹甲弾[tekkoudan] armor piercing ammunition
徹宵[tesshou] all night
徹底[tettei] thoroughness