“yet” is an adverb that means “up to now” or “so far”. It is used to emphasize that something is the most extreme or the latest in a series of events or states. It usually comes at the end of the sentence after a superlative adjective like “best”, “biggest”, “largest”, or “worst”. For example, “This is the best yet” means “This is the best so far”.
In the English Vocabulary Profile at B2,
the best/worst, etc. yet = the best or worst, etc. until now
A search in NOW CORPUS:
_A _JJT yet .
1 THE BEST YET. 843
2 THE BIGGEST YET. 321
3 HIS BEST YET. 282
4 OUR BEST YET. 194
5 THE WORST YET. 156
6 THEIR BEST YET. 106
7 HER BEST YET. 91
8 THE LARGEST YET. 86
9 ITS BEST YET. 72
10 THE TOUGHEST YET. 72
Forecasters are predicting strong winds throughout the entirety of the tournament this week,
which will make this year‘s tournament the toughest yet.
11 THE HIGHEST YET. 61
12 ITS BIGGEST YET. 46
13 HIS TOUGHEST YET. 41
14 THEIR BIGGEST YET. 41
15 HIS BIGGEST YET. 34
16 THE STRONGEST YET. 33
17 THE HARDEST YET. 32
18 MY BEST YET. 29
19 ITS LARGEST YET. 25
20 ITS HIGHEST YET. 25
21 OUR BIGGEST YET. 22
22 THE DEADLIEST YET. 20
She said she expects this surge to be the deadliest yet.
23 HIS FINEST YET. 17
24 THE BUSIEST YET. 17
25 HER BIGGEST YET. 16