What is the strongest chemical bond?
In general, covalent bond.
The covalent bond is a very directional bond, and depending of the species it has a energy ranging from 1.9 eV to 10 eV aprox. The next would be the ionic bond which involves the attraction between charged particles and the energy of the ionic bond goes from 2 eV to 6 eV aprox.
In order of increasing strength there are the types of chemical bond:
van-der-Waals bond < hydrogen bond < metallic bond < ionic bond < covalent bond.