The strength of a stand can be measured in many ways.
It is a manifestation of one's fighting spirit, one could even say... a manifestation of one's own soul. Stands can drastically improve depending on their user, and how much potential they have. Even applying their abilities to new concepts, techniques, or anything else in some cases.
Take for example, Hamon or The Spin, these can completely open up new things for a stand to do, not to mention if the stand is a close range, humanoid, or power type stand they get even stronger based on their users own physical characteristics.
Dio Brando's The World was even stronger than Jotaro Kujo's Star Platinum because of Dio's already absurd vampiric strength!
Stands are also capable of having possibly any ability because of how varied people and animals are.
Stand Stats: This is the ranking system of stands capabilities sometimes they seem off for some stands, but they do not always refer to what you think.
Take for example Whitesnake's D in Speed, that's not referring to it's physical movement or striking speed. It is referring to how fast it's acid takes affect.
Stats Guide: for Physical strength, Speed, and Persistence.
E: Human
D: Superhuman
C: Supernatural
B: Unprecedented
A: Deific
Dirty Deed's Done Dirt Cheap [D4C]
Stats:
Power: A
Speed: A
Range: C
Persistence: A
Precision: A
Potential: A
D4C has the same Statsas Star Platinum. D4C is at bare minimum as strong as Star Platinum is, however because of it's ability, it seems like it is much stronger.
Ability: D4C has an interesting and very powerful ability that has two different aspects, D4C can allow different realities to merge in one area allowing multiple points to converge.
This ability is what caused the who shot Johnny Joestar situation. In reality, all of the suspects had shot Johnny, because multiple realities were converged at one location.
The other Part of D4C's ability is to travel to different Dimensions, when put between two different things, even liquids and gasses allow D4C to use it's ability.
This ability allows Valentine a great many things, Immortality, semi teleportation, projection repulsion and immunity, cloning, infinite items, stranding things in a different world, the list goes much longer than this. The abilities not said here will be said later on.
The implications of this ability are near endless, this ability also can cause a strange phenomenon known as a menger sponge, between two existing entities or objects that are counterparts.
When this happens said objects or people are obliterated from existence, it can bypass any form of durability or defense because of the reality fixing the paradox, Valentine however is exempt from this affect, as are all clones of him seemingly.
A menger sponge is a mathematical, infinite shape, that has an infinite amount of squares, and square holes, in it. A simple, and quite accurate comparison, would be that of an M.C. Escher drawing.
D4C as well, seems to be the Battery that caused all this infinite universes to exist, it seems as though before it, they never existed.
You may wonder, "How can a stand this powerful even exist?" There is a two part answer to that, Valentine's burning will to find his father, and part of a thing beyond anyone else, the mummified heart of Jesus Christ, God The Son.
The corpse parts themselves are what created stands in the true real universe, the root universe.
Valentine can even exist in between dimensions where nothing really exists, a gap between them, as demonstrated by Love Train, which wasn't even truly an ability of D4C just something it harnessed because it's power over dimensions allowed it to.
Taking this all into consideration, Valentine hasn't even scratched the surface of what D4C is capable of. D4C is godlike in many senses of the word.