A potential is a scalar field, having a value at points in space. It is not well-defined for such a field to have multiple values at a single point, so for electric potential it is safe to say no, you cannot have
two values at a single point. It is possible, though, to define a gravitational potential as well as an electric potential; the two
different fields can be defined over the same space, but would not carry
the same values.
Potential 'steps' are likely just steep slopes; an infinite voltage
gradient, for example, means infinite electric field, which is
not realistic, nor compatible with normal matter composed of atoms...
The familiar square well potentials of quantum mechanics are... soluble
mathematically, but not entirely realistic, either.