Emerging life-threatening multidrug-resistant (MDR) species such as the species complex, (sin. ), and other species are considered as an increasing risk for human health in the near future. (1) Background: Many studies have emphasized that the increase in drug resistance can be associated with several virulence factors in and its knowledge is also essential in developing new antifungal strategies. (2) Methods: Hydrophobicity, adherence, biofilm formation, lipase activity, resistance to osmotic stress, and virulence 'in vivo' on larvae were studied in isolates of , , and with low susceptibility and resistance to fluconazole and amphotericin B. (3) Results: Intra- and interspecies variability were observed. showed high hydrophobicity and the ability to adhere to and form biofilm. was less hydrophobic, was biofilm-formation-strain-dependent, and did not show lipase activity. Larvae inoculated with isolates displayed significantly higher mortality rates than those infected with and . (4) Conclusions: The ability to adhere to and form biofilms associated with their hydrophobic capacity, to adapt to stress, and to infect within an in vivo model, observed in these non-wild-type and isolates, shows their marked virulence features. Since factors that define virulence are related to the development of the resistance of these fungi to the few antifungals available for clinical use, differences in the physiology of these cells must be considered to develop new antifungal therapies.