めったにない => Rarely N3
Degree. Level, Amount
めったに~ない => hardly; rarely; seldom N3
なければならない/なくてはならない/なければいけない/なくてはいけない/なければだめ/なくてはだめ => must N5
ないといけない / だめだ => must do; have an obligation to do ~ N4
Necessity, obligation
めったな => hardly; rarely; seldom N2
Ban
[命令「めいれい」] => Do A (command) N4
Can, Should, Must
~んがため(に)/~んがための      => in order to ~ N1
... いらいはじめて => Since... this is the first time N3
Time
~づめだ      => full of N1
ため => In order to, for N4
Purpose, target
ためしがない => is never the case; has never happened; I have never seen or heard of ~ N1
Criticize
ずくめ => completely; entirely; nothing but ~ N1