つまらない (translations)→ bad bleak boring disappoint disgusting fool foolish fucking futile goddam horrible inadequate intolerable menial pedantic peewee prosaic rubbishy tedious unexciting uninteresting wearisome wretched zilch
わかりにくい (translations)→ confusing convoluted hacky
退屈な (translations)→ enduring irksome poor prasaic tiring unlively
読みにくい (translations)→ illegible indecipherable
判読できない (translations)→ undecipherable
不可解な (translations)→ dark incomprehensible strange unaccountable
