WARNING: The following contains spoilers for Thor #10, by Donny Cates, Nic Klein, Matt Wilson, and VC's Joe Sabino, on sale now.
In Thor #9, the Odinson learned the reason why Mjolnir has been acting strange, and he inviting the return of his Odin-created human half Donald Blake so he could enter the Elder sleep in search of answers to his problems. But by enabling allowing the return of Doctor Donald Blake, Thor unknowingly invited a monster of his father's making into the kingdom of Asgard.
When Donald Blake arrives he is more powerful and angry than ever before, and he quickly dispatches some of the Marvel Universe's most powerful gods. And between what he does in Thor #9 and Thor #10, he might just be the most powerful of all Odin's children.
Immediately upon Thor's change from himself into Donald Blake, the angered human quickly defeats a Mjolnir-wielding Loki and breaks his enchanted staff, therefore preventing Thor from returning and sending him back to his Odin-created world. Following this confrontation, Blake is met by the Korbinite Thor, Beta Ray Bill, along with Lady Sif and Volstagg, a former War Thor. Once again, Blake quickly and easily dispatches the trio, along with Asgard's fiercest warriors, using his surgical expertise combined with Thor's tactical knowledge and memories to disable and disarm his foes in Thor #10.
In addition to their quick defeats, Blake also removes Odin's enchantment from Beta Ray Bill before taking his power, just like he did to the Asgardian serpent Jörmungandr. It ends with all of Asgard defeated, Thor trapped in Blake's world, and Blake setting his sights on former Thor and current Valkyrie, Jane Foster.
Despite previously being the normal and relatively insignificant human half to Thor, the long-absent Donald Blake has displayed a power that never seemed possible before. Though he is not Odin's child by traditional means, Odin did create Blake as a vessel for his son Thor, thus making him Odin's child by a technicality. While Odin has many offspring other than Loki and Thor, none are as powerful as the two MCU favorites. Blake's quick dispatching of them, along with the Asgardian serpent and Asgard's fiercest warriors, all but confirms that he would easily defeat Odin's lesser children.
Through his battles and his words, Blake reveals that ultimately three things put him above the rest of his brothers and sisters: His surgical expertise, his ability to absorb the power of other beings and his complete recollection of all Thor's memories and abilities. This Donald Blake is an amalgamation of the sheer power and tactical experience of Thor combined with his own surgical and medical expertise and a mind warped by years of isolation, which makes him an opponent that likely no being in the Marvel Universe has faced before.
For the moment, there seems to be no limit to how strong Donald Blake could be, nor does there seem to be anyone who could stop him in the foreseeable future. On his own, Blake defeated the Asgardian serpent, absorbed its power, then defeated other powerful gods like Loki, Volstagg, and Beta Ray Bill. With his sights on adding the powers of Jane Foster to his arsenal, D0nald Blake may hold the title of Odin's most powerful child for a very long time.