In whatever grading system you like but base on how you like them (out of 10, A/B/C, great/good/bad, blah blah) with consideration to character design, writing, and stuffs. Just do the characters you have an opinion on, don't have to do them all. Put some words if you feel strongly about a character one way or another.
Listing based on plot relevant:
1) Big Mom
2) Pudding
3) Katakuri
4) Brulee
5) Pekoms
6) Perospero
7) Chiffon
8) Mont-d Or
9) Oven
10) Tamago
11) Smoothie
12) Zeus
13) Prometheus
14) Daifuku
15) King Baum
16) Cracker
17) Napoleon
18) Opera
19) Galette
20) Amande
21) Diesel
22) Streusen
23) Randolph
24) Praline
25) Bobbin
25) Compote
Listing based on plot relevant:
1) Big Mom
2) Pudding
3) Katakuri
4) Brulee
5) Pekoms
6) Perospero
7) Chiffon
8) Mont-d Or
9) Oven
10) Tamago
11) Smoothie
12) Zeus
13) Prometheus
14) Daifuku
15) King Baum
16) Cracker
17) Napoleon
18) Opera
19) Galette
20) Amande
21) Diesel
22) Streusen
23) Randolph
24) Praline
25) Bobbin
25) Compote