Originally, Credence doesn't understand what's happening to him in Fantastic Beasts and Where to Find Them, and so he has no control over his powers. Ariana, emotionally scarred, is also incapable of understanding or controlling her Obscurus. However, once Grindelwald explains to Credence what's happening and introduces him to the wizarding world, Credence seems to develop more and more control over his powers. When he's given a wand at the end of Fantastic Beasts: The Crimes of Grindelwald, he's able to control his gifts to the extent that he can channel that power to destroy a mountain.
The power of an Obscurus is related to the innate power of the witch/wizard hosting it, and Grindelwald has seen just how much of that raw power Credence has. If he truly believed that the young Aurelius Dumbledore was utterly incapable of controlling it, he wouldn't risk inviting him into his own castle. The fact that he brings Credence to his side, and gives him a wand, suggests that it's possible for an Obscurial to learn to control their powers, at least to an extent - and if that's the case, it would make anyone with an Obscurus under control an extremely dangerous wizard.
Albus Dumbledore is recognized as one of the greatest and most powerful wizards of all-time. And while some of a wizard's power comes from their studies, a lot of it is innate. It's possible that Dumbledore is naturally an incredibly powerful wizard and a terrific magical scholar, but it's also possible that there is a genetic predisposition to developing an Obscurus.
While Dumbledore doesn't have the kind of traumatic childhood that Credence and Ariana did, he certainly does have plenty of trauma in his life that could contribute to an Obscurus. His sister was attacked and traumatized, he lost his mother, his father was imprisoned, and he then watched his sister die in a duel that he blames himself for causing. Dumbledore may also blame himself for killing her, as he says that he doesn't know who cast the killing curse.
Fearing that his own magic may have killed Ariana was enough to prevent Dumbledore from accepting any position of power offered to him - such as Minister Of Magic - but it could also have caused him to turn a portion of that power inward. However, it's been theorized that Ariana's Obscurus transferred to Albus at the moment of her death. In Fantastic Beasts and Where to Find Them, Newt Scamander was able to keep an Obscurus alive after its host died, which suggests it could be possible for an Obscurus to find a new host. Grindelwald, under the guise of Percival Graves, indicated that he wanted to use the Obscurus, so at least the dark wizard believes it can be done.
If this is the case, and Dumbledore has an Obscurus that he's able to control, as well as use to channel and strengthen his own magic, this may become part of the infamous duel that the Fantastic Beasts franchise is headed towards. Grindelwald may be planning to use Aurelius's Obscurial power to try and defeat Dumbledore, forcing Dumbledore to draw on the power of his own Obscurus in the duel. It would be an interesting twist for the character, and would explain why Rowling decided to create the Obscurial concept and make it such a huge part of the first film in the franchise.
Of course, Rowling may not have a master plan quite that complex, or that Credence isn't actually Dumbledore's brother, and Grindelwald is lying. Grindelwald may simply be attempting to use Credence's powers against Dumbledore because the young wizard is so strong... or there may be something else going on here entirely. Audiences will have to wait until Fantastic Beasts 3 releases in 2021 to find out exactly what's in the works for the wizarding world.