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Prince Joachim is one of the two main antagonists (along with Lope de Aguirre) in the 2021 Disney film Jungle Cruise. He is a deranged and ambitious German royal, who finances and leads a military expedition with mercenaries to claim the Tree of Life, both to aid Germany's war effort and achieve immortality.
In 1916, Dr. Lily Houghton and her brother MacGregor were requesting access to the London Archives to retrieve the Arrowhead, and as soon as Lily was about to take it herself with MacGregor stalling them with a long speech on a card, she runs into Joachim, who also has come for the Arrowhead. He points her to the Secretary's Gallery upstairs, pointing away from where the Arrowhead is being held.
Later on, he asks someone who works at the Archives to take him to the crate where the Arrowhead is being held, only to find that Lily took it and replaced the Arrowhead with a stuffed toucan. Fed up with losing the Arrowhead to Lily, he then threatens the one working in that room who Lily was and kills some of the other archive members when said member accidentally reveals his name in front of them.
A while later, he follows Lily and MacGregor to Brazil, with his men catching up and getting there before Lily and MacGregor could. His men capture Lily and try to sell her off, but she escapes with Frank Wolff after fighting them off.
Joachim gets word of Lily's escape and Frank's cruise ship, so he orders his men to arm the cannon so that he can sink the boat. He fails to sink them with the cannons, so he launches torpedos instead. His torpedos miss them due to Frank crashing into one of Nilo's boat docks and Joachim crashes into another dock after a rope gets stuck within one of the propellers.
Angered that he lost the arrowhead once again, he then plans to resurrect Lope de Aguirre by giving him some of the river water, in exchange for helping him retrieve the Arrowhead from Lily and getting the Tears of the Moon. Aguirre agrees, and Joachim detonates the cave, allowing the waters of the River to flow within the cave and reviving Aguirre's crew.
After Aguirre and his crew find some Tribesmen like the ones he fought years ago, he tries to obtain the Arrowhead from Lily. Upon failing to do so, they help Joachim find the Tree with the Tears of the Moon, and capture MacGregor along the way.
A while later, after Lily and Frank empty the water to open the cave where the Tree was being held, Joachim managed to beat them to the punch and threatens to kill MacGregor if they fail to give him a piece of the Tree's Tears. After giving the tree its powers back, Lily shoots Frank, but in doing so doesn't kill him as he's cursed like Aguirre. After he falls into the river, he takes out Joachim's men and saves Lily and the last petal.
As Frank caught the petal, Lily and MacGregor fight off Joachim one last time. MacGregor knocks Joachim into a wall which causes it to crumble down and a part of it crushes Joachim to death.
Prince Joachim often comes across as a pretty polite and even quirky man. Underneath the polite façade, however, Joachim is homicidal and greedy in nature. His underlying ruthlessness when it comes to getting what he wants is especially evident when he's holding MacGregor hostage and initially shows him a fair bit of hospitality, only to then quickly threaten to have an entire innocent tribe killed just to strong arm him into telling him the location of Lily and the arrowhead. As for his greed, this is especially apparent when he betrays Aguirre and his men by going back on their deal. Specifically, he promised them that if they helped him, he would share the petals of the Tears of the Moon with them so that they could lift their curse, only to betray them by killing the bees they were using to convey information, so that they wouldn't be able to find it once he knew the location himself so he could horde more of the petals for his own means.
Despite all of this, it's worth noting that Joachim never engages in cruelty or murder for its own sake. For example, once MacGregor told him what he needed to know with regards to where Lilly and Frank were, it's highly implied he left the tribe he threatened alone since he got what he wanted. Also, when pursuing the trio on Frank's boat earlier in the movie while in his submarine, he caused surprisingly little collateral damage despite chasing them through a port area, with the only significant damage being the destruction of an empty building owned by Nilo, with even that being caused by Frank redirecting a torpedo he fired underneath the boat. Another notable point is that on the one hand, he quickly murders a few members of the society who were planning to give him the arrowhead in exchange for a considerable sum of gold when one of them accidently reveals his name in front of a few others present, which was supposed to be kept confidential. Conversely though, he was quite forgiving and merciful towards the member he was making the transaction with for one, allowing Lilly to steal the arrowhead, and two, carelessly revealing his identity to the others. This only further emphasizes that while quite ruthless and having no qualms with killing or threatening innocent people to get what he's after, he does so specifically when it's a means to an end, but won't go out of his way to do it either when he doesn't deem it necessary.
Although he and Aguirre were main antagonists, Joachim had more screen time and was the one responsible for the events that almost damaged the tree.
In real life, Joachim spoke no English and killed himself in 1920.