Lethal Weapon 4 (1998), directed by Richard Donner, sends Riggs and Murtaugh against a Chinese crime lord who smuggles families into the country and uses them as slave labour. Mel Gibson plays Riggs, now facing fatherhood. Danny Glover plays Murtaugh, still too old for this.
Lethal Weapon 3 (1992), directed by Richard Donner, follows Riggs and Murtaugh as they chase a former police officer who steals confiscated weapons and sells them on the streets. Mel Gibson plays Riggs, who meets his match in a tough internal affairs sergeant.
Lethal Weapon 2 (1989), directed by Richard Donner, sends Riggs and Murtaugh against South African diplomats who use their immunity to run a drug operation in Los Angeles. Mel Gibson plays Riggs, now steadier but still willing to cross any line.