Proton plus complex anion complexes must be prepared in ‘exotic’ solvents such as liquid SO2 and where the complex anion has fluoride ion ligands.
George Olah's 'magic acid' is prepared by mixing antimony pentafluoride and fluorosulfonic acid. Hydrocarbon wax will dissolve in a magic acid solution.
Such complexes are the strongest Brønsted acids known. Super [Brønsted] acids, 'superacids', have pKa values in the region -15 to -25, ie they are up to 20 orders of magnitude more [Brønsted] acidic than sulfuric acid.
Superacids are able to fully protonate all Lewis base organic functional groups (as opposed to protonating a low equilibrium concentration). Alkenes, benzene, carbonyls and nitro functional groups are all protonated by superacids. For example:
Read more on the Wikipedia superacid page.