You must not confuse at last and at least.
At last means "finally" and at least means
"at any rate" or "at the minimum".
· At last is put either before a clause (at the
beginning of a sentence for example),
either after the auxiliary or at the end of
the sentence.
Example:
At last you have stopped that noise.
I can at last manage this.
We've arrived at last.
Insusceptible