Both main male leads are the self-sacrificing sort that have more lives than a cat, both are in love with a childhood fried who is the source of at least half of their troubles.
Both have a similar plot where the death of someone close to them causes the main characters to seek revenge. As the story progresses, the characters begin to learn more about the past and the events behind their loved one's death, and the only people they can trust are each other.
They both have somewhat similar plot about a cop doing an undercover work in a triad. Both also gave me some sorta same feeling and both are great movies filled with action.
In both, you have the subject of NIS agents going undercover. You also have a love story in both. TBDW is more serious and dramatic than 7th Grade, which is more built like a romantic comedy.