Low-energy damped collisions of very heavy nuclei (238 U +238 U , 232 Th +250 Cf and 238 U +248 Cm ) are investigated within the realistic model based on multi-dimensional Langevin equations. Large charge and mass transfer was found in these reactions due to the inverse (anti-symmetrizing) quasi-fission process leading to formation of survived superheavy long-lived neutron-rich nuclei. In many events lifetime of the composite system consisting of two touching nuclei (giant quasi-atoms) turns out to be rather long; sufficient for spontaneous positron formation from a super-strong electric field, a fundamental QED process.