The fatser it moves the heavier it is

In Newtonian mechanics when a constant force acts on a body for a long time it's velocity keeps on increasing and even goes faster than speed of light. Whereas in relativity, the body keeps on increasing its momentum, not "speed", which can continuously increase because mass can increase.

After sometime there will be no acceleration in sense of velocity, the object keeps on getting heavier, so much so the relativistic mass booms to infinity if a object tries to equal it's velocity to the speed of light which is known to be not possible for various reasons one of them is that an objects mass can't be infinite.

If we consider a special case of synchrotron, the high speed electrons need 2000 times stronger magnetic field from what Newton's laws expects it to be, So it's evident that electron's relativistic mass is 2000 times heavier. That is almost more than mass of a proton, If we work out the math the electron's velocity differs from speed of light by one part in 8000,000, So it's almost nearer to the speed of light. If there was a 700m run between high speed electron and light, the light would reach the finish line ahead by just ¼ the thickness of a piece of paper!

When the electrons are going that fast their masses are enormous but their speed can't go beyond the speed of light. So to conclude the faster an object tries to move the heavier it becomes the greater is it's inertia.

An electron can beat visible light in air, but it's because of refractive index. However, Gamma Ray still outruns it.