How close to the light speed would, say an electron (the lightest particle with a measured nonzero mass of (511 keV/c²) travel if you pumped all the mass-energy in the observable universe into it (4×10 to the 69th power Joules)?Just curious, as these particle speeds may have been in the first moments after Big Bang.

BTW. when after the BB did the leptons form?I have info about quarks and atoms, but no idea about leptons.