Step 1: Species of Plasmodium infecting humans.
1. Plasmodium vivax
2. Plasmodium malariae
3. Plasmodium ovale
4. Plasmodium falciparum
Step 2: Malignant malaria.
Plasmodium falciparum causes malignant malaria (cerebral malaria), the most dangerous form with high fatality.
Step 3: Conclusion.
Thus, Plasmodium falciparum is responsible for malignant malaria.