なくてはいけない => Must do A; have to A N4
Can, Should, Must
てはいけない => May not A, must not A N4
Can, Should, Must
[決「けっ」]して~ない => Won’t, isn’t N3
Will, Decision, Doing
わけにはいかない => Must not A, Must A N3
Needs, Requirement
なければならない => Must do A; have to A N4
Can, Should, Must
と([思「おも」]う、[言「い」]う、[考「かんが」]える) => That A N4
Particles
と[思「おも」]いきや => Even though A (was thought/expected), different result B N1
Contrast/Surprise
て[頂「いただ」]けないでしょうか? => Could you please A for me? N4
Secondary Verb
だけではすまない => Doing A is not going to suffice N1
Miscellaneous
わけがない => There's no reason for A (A should not be possible) N3
Potential, Possibility
わけではない => Although you may think A, that is not the case. N3
Contrast
ないものでもない/ないでもない => A is not completely impossible N1
Need/Requirements