Błędnie: He died, and to make the matters worse, he did not leave his will. Poprawnie: He died, and to make matters worse, he did not leave his will.
Zwrot ‘to make matters worse’ („na domiar złego”) to idiom, nie można więc go w jakikolwiek sposób zmieniać. Np. ‘To make matters worse she lost her passport as well’ („Na domiar złego zgubiła też paszport”).