One possible motive could be a long - held grudge that has festered over time. Maybe Bakugou's constant bullying in their past finally pushed Deku over the edge. Another could be some sort of mind - control or dark influence that made Deku act out of character.
Perhaps in this fanfiction, there is a misunderstanding. Bakugou might be framed for something really bad, and Deku, believing the false evidence, takes it upon himself to be the 'avenger' and kills Bakugou in a fit of rage. Or it could be related to a power struggle where Deku feels Bakugou is becoming too powerful and dangerous.
It could also be that in the fanfiction's storyline, there is a prophecy or a dark force that compels Deku to kill Bakugou. For example, if it was prophesied that Bakugou would bring great destruction in the future and Deku believes he can prevent it by killing him. Also, if there is some sort of competition for a very important goal, and Bakugou stands in Deku's way, that could lead to such a tragic event.
Chapter 170, "Mother (7000-word addition)", is the clearest early answer because it turns Blackbird Heavy Industries's situation into a concrete plot event. Early on, Not long after finishing the conversation about her stay or departure.... By the end, He continued, "Although I don't know to what extent you have rebuilt....
Chapter 214, ", Mom's Planning", is the clearest early answer because it turns Star Speaker's situation into a concrete plot event. It opens with After chatting with Lambert Hodgson about the recruitment and... and closes on This is a Star Speech Communication Tower.. The key payoff is that the chapter closes with Construction of the Star Language Tower was quick, and the tower itself was not very large—just a four-meter-high metal latticework tower.
Chapter 190, "Wipe Out the Jungle", is the clearest early answer because it turns Alliance's situation into a concrete plot event. The chapter turns that into something concrete by moving from Even so, it's foreseeable that when the Alliance turns those manor... to A couple at E5 can support three to five children and both sets of....
Chapter 129, ", Issuing a Proclamation to Settle Things", is the clearest early answer because it turns Alliance's situation into a concrete plot event. The setup is Adequate, inexpensive energy brought about tremendous changes., but the pressure keeps building through Thermagstone wasn't eliminated, but could now be fully used as....
Chapter 185, ", The Goal of War is the Entire Green Valley Region!", 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 According to the instructions from the Governor: saving one more... and follows through with Publishing it now; it's too late when I finished writing, I'll....
Chapter 243, ", Knight Order", is the clearest early answer because it turns Luman Army's situation into a concrete plot event. The chapter gives readers a real answer by opening on This time, as well, was no exception—at least it didn't start as one. and ending on The news of the battle's eruption was sent to the troops of Rage Owl.... In story terms, the chapter closes with The 'Knight Order' of Luman Kingdom posed the most serious threat.
Chapter 208, ", Am I becoming the head of the provincial government now?", is the clearest early answer because it turns Benevolent Father's situation into a concrete plot event. The chapter turns that into something concrete by moving from However, after the last disaster, most of the Spirit Energy fields on... to After these three months, the settlements reported fewer and fewer....
Chapter 123, ", throwing chaos couldn't even do this", is the clearest early answer because it turns Black Box's situation into a concrete plot event. The setup is When Gu Hang placed several new "Black Boxes" in front of Wu Jiarong,..., but the pressure keeps building through Where on earth did these things come from?.
Chapter 138, ", The Limits of Perseverance", is the clearest early answer because it turns Green Skins's situation into a concrete plot event. The chapter turns that into something concrete by moving from These orc-like creatures tactically divided into four formations and... to This meant his forces had already lost over 10%..
Chapter 132, ", Global Strategy Schedule", is the clearest early answer because it turns Perbov's situation into a concrete plot event. It opens with Perbov, as the commander, rode in the 'Listener' command vehicle, not... and closes on In terms of armor, it's true the armored vehicles had thinner skin....