"Damn it!"
The Batman Who Laughs had just gone all in on the biggest haul he could seize in a single move in his entire life, only for Batman Dragon to immediately bite back and make him suffer the greatest loss he had ever experienced.
The finger Perpetua had willingly given him had allowed him to analyze her power of creation in almost no time at all. As long as he found the Total Aggregate before Perpetua did, he could use this finger to unlock the Total Aggregate's seven powers—more importantly, he could bypass Perpetua entirely!
Originally, he had been helpless against the Total Aggregate. Even if he obtained it, it would be useless to him. His original plan had been to lure the Prime Universe's Lex Luthor into submitting to Perpetua, then guide Luther from the shadows to devour Martian Manhunter. In the end, this would allow him to unlock the Total Aggregate and release all its power. That meant that, to complete his plan, The Batman Who Laughs would ultimately still have to find a way to replace Luther and become Perpetua's representative...
(Note: This follows the original Death Metal plot. The Batman Who Laughs heard Perpetua's whispers from Barbatos long ago, then told Lex Luthor the secrets of the Source Wall, all to manipulate him and seize control of the timing of Perpetua's release. The Batman Who Laughs had always been hiding in the Prime Universe's Luther's shadow. It could be said that he had been playing Luther in the palm of his hand.)
Originally, this would not have been difficult. He had been completely confident that he could kick Luther out at the most critical moment. From beginning to end, Luther had merely been his stand-in. Everything had been part of The Batman Who Laughs's plan.