This 'Godzilla' should be THE godzilla featured in the films Godzilla, and Godzilla, King of The Monsters. Of course, the main issue will be the atomic breath. Is it physically possible, with mastery of genetic modification, to be able to create such a creature? Note-the 'atomic breath' doesnt have to be radioactive, it just has to deal a obscene amount of damage to anything in it's path.
The size, for a start, makes it completely impossible for a bipedal creature. A whale that size might conceivably work, but supporting its own weight as Godzilla does would be impossible.
The atomic breath would be impossible because 'atomic breath' is not a thing. Exhaling radioactive gas would be another matter but would not give the effect you are after.