In the English Vocabulary Profile, listed at B1 is:
get worse = to become more ill, unpleasant, difficult, severe, etc. than before
For example:
But if this thing gets worse, we must close.
There is no English Grammar Profile point that specifically focuses on GET + comparative
A search in NOW corpus for:
GET _JJR
1 GET WORSE 42282
2 GETTING WORSE 27902
3 GET BETTER 25497
4 GET OLDER 22394
5 GOT WORSE 12158
6 GETTING OLDER 11160
7 GET BIGGER 10316
8 GETS WORSE 10298
9 GETTING BIGGER 10198
10 GOT OLDER 9358
11 GET STRONGER 8312
12 GETTING STRONGER 8241
13 GETTING BETTER 7161
14 GET HIGHER 4797
15 GETS BETTER 4545
16 GETS OLDER 4112
17 GOT BIGGER 4079
18 GETTING SMALLER 3811
19 GET TOUGHER 3564
20 GETS BIGGER 3263
21 GET RICHER 3057
22 GETTING HARDER 3036
23 GOT BETTER 2796
24 GETTING RICHER 2559
25 GETTING HIGHER 2547
26 GET CHEAPER 2485
27 GET SMALLER 2423
28 GOT STRONGER 2230
29 GETTING YOUNGER 2197
30 GETTING TOUGHER 2193
31 GET SMARTER 2190
They get smarter the more you interact with them.
32 GET FURTHER 2130
33 GOTTEN OLDER 1916
34 GETS STRONGER 1815
35 GETS HARDER 1801
36 GETTING LOUDER 1788
37 GETTING SMARTER 1743
38 GETTING WARMER 1706
39 GETTING SHORTER 1633
40 GET GREATER 1626
41 GET LOWER 1625
42 GET LARGER 1594
43 GET YOUNGER 1535
44 GETTING HOTTER 1513
45 GETTING CHEAPER 1500
46 GETTING LARGER 1370
47 GETTING POORER 1326
48 GET FITTER 1244
49 GETS TOUGHER 1207
50 GOTTEN BIGGER 1201
51 GETS WARMER 1149
52 GET HEALTHIER 1128
53 GETS COLDER 1114
54 GET LOUDER 1097
55 GETTING WEAKER 1077
Not only has that been weak, it‘s getting weaker.
56 GET EASIER 1061
57 GET SHORTER 1046
58 GETS SMALLER 1035
59 GETTING LOWER 981
60 GET HOTTER 978
61 GOTTEN STRONGER 933
62 GET WARMER 920
63 GETTING COLDER 903
64 GETTING TIGHTER 893
65 GET POORER 871
66 GET BUSIER 856
67 GETTING BUSIER 855
68 GET FASTER 837
69 GOT SMALLER 833
70 GET COLDER 823
71 GETTING HEALTHIER 818
72 GOT TOUGHER 809
73 GOT LOUDER 776
74 GETS EASIER 772
75 GETTING WIDER 768
76 GETTING CLOSER 765
77 GETS HIGHER 757
78 GETS CLOSER 746
79 GETS HOTTER 740
80 GOT HIGHER 720
81 GOT RICHER 698
82 GET DARKER 640
83 GETTING SICKER 622
84 GETTING EASIER 605
85 GET WEAKER 588
86 GET HARDER 582
87 GETTING DARKER 582
88 GET TIGHTER 567
89 GETTING HEAVIER 567
90 GETS LARGER 566
91 GETTING FITTER 555
92 GETTING THINNER 544
93 GET WIDER 524
94 GETS LOUDER 516
95 GETS DARKER 502
96 GETTING BRIGHTER 502
97 GET HEAVIER 501
98 GET SICKER 490
99 GETTING FATTER 476
100 GOTTEN SMALLER 476