The Flash
1. Barry Allen, the flash, was an ordinary scientist who was struck by lighting which gave him superhuman speed and other abilities.
2. Most of the villains in the show have superhuman abilities and were from various timelines and universes.
3. The Flash and his team do not necessarily kill the villains in their city but lock them up instead.
Arrow
1. Oliver Queen, the Arrow, was a famous billionaire who got trapped on an island where he learned his archery and combat skills.
2. The Arrow mostly fights ordinary people who seek atrocities and are associated with illegal activities.
3. The Arrow took revenge on his father's enemies by killing them, but as the show progresses, he shifted his ways and just exposed and captured the enemies for the police.
Similarities:
1. Both protagonists are heroes who fight villains to save their respective cities.
2. There are crossovers between the two shows, wherein sometimes, the Arrow and the Flash work together.
3. The Arrow and the Flash have friends and a team who support them
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