I can’t stand these two…
I’ve reviewed the ‘Not yet’ 50 times and ‘The End’ kanji/vocabulary about 200+ times between them.
I only recently figured out a way I could remember them. If you focus only on the widest vertical stroke in both Kanji you can think of it making a journey heading upwards.
For 未 the widest vertical bar hasn’t reached the top of character, it is ‘Not Yet’ there.
For 末 the widest vertical bar has reached the top of the character, therefore it has reached ‘The End’.
As for memorised the readings, 未 looks like a MIG fighter jet (み/MIi).