There could be many out there, but it's hard to single out specific popular ones. Some might be based on unique interpretations of their characters' personalities and how they interact. You could also try searching on fanfiction.net, but be aware that the quality can vary greatly.
Finding the popular Megaman X Bass yaoi fanfiction can be a bit of a hunt. You might want to check out some fan communities dedicated to Megaman. These communities often share and discuss their favorite fanfictions, and through that, you may discover some great stories about Megaman X and Bass in a yaoi relationship.
Chapter 130, "The New Deceitful Monster", is the clearest early answer because it turns Wooden Puppet Monster's situation into a concrete plot event. It opens with That scream was so shrill it startled many people outside the cabin. and closes on According to He Meng's style, the Mirror Immortal Camp will likely.... The key payoff is that the chapter closes with "To counter soldiers with generals, water with soil.
Chapter 491, "Battle On The Sea II", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on Behind them, Garrick was still fighting. and ending on One demon raised its hand, summoning a spinning vortex of water that.... In story terms, the danger stops being abstract and the conflict around trade and resources becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 19, "The Battle of the Mane Wolves", is the clearest early answer because the buildup finally cashes out in a real clash. A useful checkpoint is the way the scene starts with As the sound of beast hooves arose, Xia Hong and the others hurriedly... and follows through with And then, what happened next, further astounded them beyond belief..
Chapter 47, "Despair", is the clearest early answer because it turns Sun Xinzhu's situation into a concrete plot event. Early on, The corpses of Wang Ming and the other three, along with the knife.... By the end, Almost instantly, Shi Qing was bound by the white thread.. Inside the broader battle storyline, the chapter closes with The immense pain gradually turned into deep despair., which gives Sun Xinzhu a stronger narrative position and pushes the trade and resources onward.
Chapter 40, "Contradiction [Continue to ask for follow-up!]", is the clearest early answer because it turns Li Hu's situation into a concrete plot event. The chapter turns that into something concrete by moving from Taking such great risks to help you worthless lot deal with the... to In the past half month, the combined four camps have lost twenty-nine....
Chapter 382, "ElderGlow's Victory", is the clearest early answer because it turns Elias's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Three pulses exploded from the triangle behind Elias — one... and follows through with Saw Daveon's grin fighting for its life..
Chapter 126, "The Great Xia Calendar Officially Commences", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The birth of Yue Yuan added a lot to this great victory. and follows through with Didn't you draw the Rat King up the tree before and wounded it with a....
Chapter 500, "Getting Information", is the clearest early answer because it turns Damien's situation into a concrete plot event. The setup is Its chest rose and fell in shallow, uneven motions, every inhale..., but the pressure keeps building through Its once-proud frame was broken, limbs bent at wrong angles, demonic....
Chapter 531, "Make Them Come To Us", is the clearest early answer because it turns Mana's situation into a concrete plot event. The setup is The Forest of Twin Disasters did not forgive carelessness., but the pressure keeps building through For days now, two demon strongholds had been searching the forest....
Chapter 108, "Long-tailed Rodent [3-in-1 Mega Chapter]", 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 Xia Hong leaped to block on Luo Yuan's left side, only exchanging a... and ending on Leader, it's trying to run!" Before he could relax for long, Xia Hong....