The Lotus from Warframe might be the most powerful. She has a vast knowledge of the Orokin technology and the secrets of the Warframes. In a crossover, she could potentially control the Destiny universe's technology as well. She could manipulate the Light or the Vex network with her intelligence. Also, she has the ability to guide the Tenno, and in a crossover, she could lead both the Tenno and the Guardians against any threat that emerges from the combined universes.
I think the Destiny Hunter class has a good chance of being very powerful in a crossover. Hunters are known for their agility and stealth. In the Warframe universe, they could use their stealth to infiltrate Orokin facilities or sneak up on Sentients. They also have a wide range of powerful guns that could be modified with Warframe technology for even more destruction.
Chapter 346, "Elite Warriors, One Against Three, The Cause of the Beast Tide [10,000-Word Chapter, Continued Tomorrow]", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter turns that into something concrete by moving from Nowadays, any of these six armies alone, placed five years ago, would... to Thus, in Great Xia, it's a comparison of who breaks through more....
Chapter 166, "Daniu Gets Jealous!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event.
Chapter 327, "Beast Tide Showdown, the Wolf King’s Gambit, and White Dew Gu’s Last Stand", is the clearest early answer because it turns Xia Chuan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The thunderous roar came from the flanks of the depression. and follows through with The allure of the Cold Ruins Tripod was strong, but the deadly threat....
Chapter 340, "Seclusion, Growing Yu Generation, Family Banquet, Rapid Development", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter gives readers a real answer by opening on As the night of the tenth day of September descended, Lu Yang set out... and ending on Though Xu Ning and Lu Yang are not extraordinarily strong, they have....
Chapter 111, "From now on, Zhao Daniu is my new brother!", is the clearest early answer because it turns Shu Yan's situation into a concrete plot event. It opens with The main room's door was pushed open just a crack, and the head of... and closes on This time it was in a dream..
Chapter 77, "Why are you sabotaging me again?", is the clearest early answer because it turns Mushroom Soup's situation into a concrete plot event. The chapter gives readers a real answer by opening on Wen Jiaojiao's reminder calmed Shu Yan down.
Chapter 348, "Schemes and Counter-Schemes, the Five of East Ridge, Zhu Yang's Threat, The Dust Settles (Part 4)", is the clearest early answer because it turns Zhu Yang's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Upon hearing that Yanggu had sent someone first, Lu Yang raised his... and follows through with Once Hong Yang replaced him as the platform leader, Zhu Ling couldn't....
Chapter 233, "Individual, Ten, Hundred, Thousand... Million, Ten Million, Damn!!!", is the clearest early answer because it turns Tianyi's situation into a concrete plot event. The chapter turns that into something concrete by moving from [What the hell, what's this about life span ending??
Chapter 29, "The 36 Strategies - Sneak through Chen Cang", is the clearest early answer because it turns Jiang Shixu's situation into a concrete plot event.
Chapter 343, "Five Rounds of Bone Tempering, One Thousand Bristles Bone Burning in the Visible Yang Realm", is the clearest early answer because Mother Stele finally turns buildup into a real advancement. Early on, Hong Ye and the Zhao family members happened to be walking below the.... By the end, Thus, he didn't rush the breakthrough but boldly attempted a second....