Fullmetal Alchemist: Brotherhood is an action fantasy series that stars Edward Elric, the Fullmetal Alchemist himself, and his quest to make amends for his attempt at human transmutation. He may have lost his mother, but he and his brother Alphonse still have their estranged father, Van Hohenheim, to deal with. They have an odd relationship with him, to say the least.
Van Hohenheim is more than he seems. He is centuries old, and he came from the now-defunct desert empire of Xerxes, where he worked as a slave until he was taught how to perform alchemy. Hohenheim is wise and well-read, and he is crafty, too. But sometimes, even he might make a mistake or get the wrong idea about what's going on.
10 WAS RIGHT: Spreading Alchemy To Xing
In the Chinese-inspired nation of Xing, the people perform a variant of alchemy known as alkahestry, which can modify matter from a distance, so long as a pentagram within a circle is drawn. May Chang demonstrated this ability, which is a sort of remote alchemy.
But more than anything, alkahestry is a healing art, one that was unknown in Xing until Hohenheim shared alchemy with the people of Xing during his many years of wandering the world. Now many people can heal each other with Hohenheim's gifts.
9 WAS WRONG: Trusting The Homunculus
A few centuries ago, the powerful homunculus known as Father was simply a tiny creature inside a glass container, known as "the dwarf in the flask." This cunning creature spoke to Slave #23 one day and gave him the name Van Hohenheim, along with the secrets of alchemy.
But this was all a ploy. The dwarf homunculus conspired to become a godly figure, and it manipulated Hohenheim into creating a massive transmutation circle, with the aid of other Xerxes workers. Then, when the transmutation was complete, all of Xerxes was sacrificed to make Father stronger.
8 WAS RIGHT: Sealing Pride Away
Pride the homunculus was Father's most powerful minion, and he and his fellow homunculus Gluttony faced Edward, Al, Hohenheim, the Xingese warriors, and others during a forest battle. At some point, Hohenheim realized that there was only one way to deal with Pride.
Unable to destroy Pride entirely, Hohenheim opted to create a dense dome of the earth to contain Pride inside, where the complete darkness would restrain Pride's powers. Alphonse ended up inside there too, and he confirmed that Pride was powerless.
7 WAS WRONG: Letting Pride Escape
Then again, there might have been a weak point in Hohenheim's otherwise solid plan. Alphonse was indeed inside the earth dome to watch over Pride, and Pride would be powerless until the Promised Day was over. But Pride has help from the outside.
At some point, Solf. J. Kimblee received Pride's Morse code distress signal, and he blasted Pride free. Hohenheim ought to have realized that Father would have other minions to call upon, and there should have been more guards around Pride's earth prison.
6 WAS RIGHT: Confirming Pride's Presence In The Tunnel
Pride's shadow body primarily existed inside the circular tunnel that the homunculus Sloth had dug around Amestris and that tunneled under Liore, a town that the Elric brothers once visited. Hohenheim arrived, and he heard about a strange tunnel under the town. He went to go check it out.
Hohenheim wisely told his new friends to stay back, and he visited the tunnel alone and faced Pride in there. Hohenheim scoffed at Pride's arrogant claims and asserted his faith in his family and humanity as a whole. Hohenheim returned unharmed and made sure that no one else could go where he had just gone.
5 WAS WRONG: Calling Himself A Monster
Van Hohenheim dedicated most of his time to plotting Father's downfall or spreading knowledge of alchemy, but he did find time for love, too. He married the human woman Trisha Elric and had two sons with her, but even then, Hohenheim felt like an outsider. A freak, even.
Hohenheim saw himself as a monster due to his long lifespan and status as a human Philosopher's Stone. But Trisha told him that he was a beloved part of the family, not a monster, and Hohenheim was moved to tears when he realized that Trisha was right.
4 WAS RIGHT: On Why, Ed & Al Fled Home
When Ed and Al committed the grave sin of human alchemy, they lost some body parts, and they had to live with the shame of what they had done. So, the brothers got metal replacements for what they lost, and to show their resolve, they burned the family house down and started their adventure.
But that wasn't the only real reason for their drastic plan. Hohenheim, when he met Ed again, correctly pointed out that Ed and Al were running away, desperately trying to hide their shameful past and distance themselves from it. Ed was speechless when Hohenheim told him this.
3 WAS WRONG: Antagonizing Ed Too Much
Then again, Hohenheim could have been a little gentler when he provided his insights into Ed and Al's journey. Edward is indeed rather antagonistic to his father, but in all honesty, Hohenheim could have done more to bridge the gulf between them.
After all, Hohenheim got along better with his younger son, Alphonse, which shows that he can be gentle and understanding with his sons. Given Ed's vital role in the world around him, Hohenheim should have been a bit more diplomatic.
2 WAS RIGHT: Preparing For The Promised Day
Van Hohenheim knew that Father was out there, and he was determined to foil his doppelganger's plans no matter what. So, for many years, Hohenheim wandered the world in a circular pattern, planting spare souls from his Philosopher's Stone in the intersection points of a vast transmutation circle.
When the Promised Day came and Father's giant circle activated, it absorbed the souls of tens of millions of people. That was when Hohenheim sprung his trap, and he used his own carefully-laid souls to undo what Father had done and return the stolen souls to their original bodies. Defeating Father would have been much more difficult otherwise.
1 WAS WRONG: Abandoning Trisha
During his married years, Hohenheim was still active, and he was wandering the entire world, the same as always. Edward resented his father's long stretches of absence, though Trisha didn't mind as much. Then she fell ill and died while her husband was who knows where.
Hohenheim couldn't have predicted this with 100% accuracy. However, perhaps he was spending too much time away from home, and Pinako Rockbell (Winry Rockbell's grandmother) also lamented Trisha's death due to Hohenheim's absence. Now, all Hohenheim can do is visit Trisha's grave and wonder, in futility, why she had to die on him. Perhaps he could have helped prevent this?