The final showdown would be a key event. Loki, having prepared everything, faces Thanos. It could be an intense battle of wits and powers, with Loki using all his tricks and the knowledge he has gained throughout the story to finally stop Thanos and save the universe.
There might be a moment where Loki discovers a crucial piece of information about Thanos. For example, he finds out the true source of Thanos' power and figures out how to cut it off. This discovery could be a turning point in the fanfiction.
Another possibility is that Loki teams up with other characters. He could form an alliance with the Avengers or some other powerful beings in the universe. Together, they could come up with a plan to stop Thanos. Loki could contribute his unique skills, like his ability to shapeshift and infiltrate Thanos' ranks, and then they could launch a coordinated attack.
The plot could start with Thanos arriving in the wizarding world. Harry senses the great danger he poses. Harry would first try to understand Thanos' powers and motives. He might gather information from the Ministry of Magic's records or from ancient magical texts. Then, he would start to form a team of wizards and witches who are willing to fight. As the story progresses, they would engage in battles with Thanos and his minions. Harry would use his Patronus charm to protect his team from Thanos' dark energy, and he would gradually figure out a way to stop Thanos, perhaps by using a combination of powerful spells and the unique magical environment of the wizarding world.
The key events include his birth on Titan. Then his realization about the 'problems' in the universe which led to his obsession with the Infinity Stones. Another major event was when he managed to collect all the Infinity Stones and snapped his fingers, causing the decimation of half of all life. And of course, his final defeat by the Avengers.
Loki could also show signs of fear, though he would try to hide it. Inside, he knows the power that Thanos wields. But on the outside, he would maintain a facade of bravado. His reactions would be a mix of his natural cunning and the instinct to survive in a very dangerous situation.
Well, one possible plot could be that Thanos uses his mind - controlling powers on Loki to make him steal powerful artifacts for his collection. Loki, being under Thanos' control, has to go against his own nature at times. For example, he might have to target Asgardian relics that he would otherwise protect.
Power is a common theme. Both Thanos and Loki are power - hungry in their own ways. In fanfictions, they often either compete for power or try to use each other's power for their own goals. Another theme is redemption. Sometimes Loki is seen as a way for Thanos to find redemption, or vice versa.
Well, perhaps Harry could use his magic skills like the Patronus charm to hold Loki at bay. Since Harry has experience dealing with dark forces, he might be able to outwit Loki's trickery.
Maybe Harry Potter could stop Thanos with the help of his friends. Hermione's intelligence could come up with a plan. They could use time - turners to go back in time and prevent Thanos from getting the Infinity Stones in the first place. Ron could be there for moral support and also use his chess - playing skills to outwit Thanos in some strategic battles.
Another scenario could be that Loki forms an unexpected alliance while in captivity. He could meet some other captives who have a grudge against Thanos. Together, they could plot against Thanos from the inside. Loki's silver tongue might be able to convince these captives to trust him and follow his lead. They could create a distraction or a mutiny within Thanos' forces, which would give Loki an opportunity to either escape or turn the tables on Thanos.
In a Loki x Thanos mpreg fanfiction, a potential plotline could be that the pregnancy is part of a prophecy. Loki and Thanos have to deal with the implications of this prophecy, whether it means the child will bring great power or destruction. There could be a lot of internal struggle for Loki as he contemplates his role as a soon - to - be parent, especially considering Thanos' nature. And Thanos could be using the situation to gain an advantage over his enemies, all while trying to protect Loki and the unborn from those who would oppose them.