Love against all odds is also a popular theme. Given Thanos' actions in the Marvel universe, it's quite a stretch for a relationship with a reader to develop. But fanfictions often explore this, showing how love can potentially overcome his dark nature and the differences between them. It's a theme that allows for a lot of creative exploration.
Redemption is another theme. Some fanfictions explore the idea of Thanos being redeemed through his relationship with the reader. The reader might see something good in him that others don't, and try to bring out that side. This can lead to some very interesting character development arcs.
Power is a common theme. Thanos is extremely powerful and Wanda has her chaos magic. Fanfictions often explore how their powers interact or clash. For example, in some stories, Thanos may try to control Wanda's power for his own ends.
A common theme is the clash of ideologies. Thanos with his view of 'balancing the universe' and Tony, the defender of Earth. Their different beliefs often lead to intense confrontations and debates within the fanfictions.
Redemption can also be a theme. Maybe the OC tries to bring out a different side of Thanos, a more humane or less tyrannical side. This often involves a complex relationship development between the two characters in the fanfiction.
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.
The idea of an unlikely friendship or more can be a theme. Since they are from different worlds in the Marvel universe, seeing how they come together and form a bond, whether it's platonic or romantic, is a theme that many fanfics might explore. For example, they could team up against a common enemy that neither could face alone, and during that time, their relationship develops.
A sense of belonging is another big theme. The reader, who may feel like an outsider in the real world, finds a place where they belong among the mutants. There are also themes related to fighting for justice, just like the X - Men do in the original stories.
Power is a common theme. Thanos is extremely powerful and Loki is always seeking more power, so fanfics often explore how they interact in terms of power - whether it's a power struggle or a shared pursuit of power.
One common theme is the power dynamic. Since Thanos is so powerful, the fanfics often explore how the OC either challenges that power or is in awe of it. For example, in many stories, the OC might try to resist Thanos' tyrannical ways, creating a tense and interesting power struggle.
One common theme is adventure. Since Chekov is part of the Star Trek universe, many fanfictions involve the reader going on adventures with him through space, exploring new planets and facing various challenges.
Love and sacrifice are also very common. The reader might fall in love with Vergil and be willing to sacrifice for him, or vice versa. In some fanfictions, there is also the theme of discovery. The reader discovers new sides of Vergil that no one else has seen, which deepens their relationship.