Disruption of cell membranes is a basic host protection response present in nearly all types of life. The molecular mechanisms range however usually result in energetically favored round nanopores. Right here, we report an elaborate fractal rupture sample induced by a single side-chain mutation in ultrashort (eight–11-mers) helical peptides, which in any other case kind transmembrane pores. In distinction to identified mechanisms, this mode of membrane disruption is restricted to the higher leaflet of the bilayer the place it reveals propagating fronts of peptide-lipid interfaces which are strikingly just like viscous instabilities in fluid circulate. The 2 distinct disruption modes, pores and fractal patterns, are each strongly antimicrobial, however solely the fractal rupture is nonhemolytic. The outcomes provide broad implications for elucidating differential membrane concentrating on phenomena outlined on the nanoscale.