1:- "last but not the least" It's used when we are talking about several things - or more usually people - and we want to point out that just because we are talking about this thing or person last, it doesn't mean they are the least important. It can be used humorously, or more often to avoid offending whoever was last on your list. 2:- "least but not the last" - doesn't have any meaning and is not used.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.