The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes respiratory disorders, with disease severity ranging from asymptomatic to critical manifestations. The current retrospective study compared the efficacies of different antiviral regimens used in patients suffering from severe COVID-19 disease from 19 January 2020 to December 2021 in a single center in Saudi Arabia. In total, 188 patients were enrolled in the current study, including 158 patients treated with different antiviral regimens, and 30 who did not receive any antiviral treatment. Different antiviral regimens, including favipiravir, remdesivir, oseltamivir, favipiravir/remdesivir, and favipiravir/oseltamivir were adopted. The effects of using different antivirals and antibiotics on the survival rate were evaluated, as well as the presence of comorbidities. Among all severely affected patients, 39/188 (20.7%) survived. Both age and comorbidities, including diabetes and hypertension, were significantly correlated with high case fatality following SARS-CoV-2 infection. Remdesivir alone and the combination of favipiravir and remdesivir increased the survival rate. Surprisingly, both imipenem and linezolid helped in the deterioration of disease outcome in the patients. A negative correlation was detected between increased mortality and the use of favipiravir and the use of either imipenem or linezolid. Among the compared antiviral regimens used in the treatment of severe COVID-19, remdesivir was found to be an effective antiviral that reduces COVID-19 case fatality. Antibiotic treatment using imipenem and/or linezolid should be carefully re-evaluated.