Like countless Hollywood franchises, "Lethal Weapon" is a series of diminishing returns. With this fourth installment, the cast appears so relaxed and out of character, it's like the actors didn't realize the cameras were rolling. And yet, twenty years later, the film's sturdy craftsmanship and commitment to practical stunts register as a breath of fresh air. A star-making turn from Jet Li doesn't hurt either.
Sure, it still has some great moments and the interaction between the two main characters is still great but it's not enough to carry the whole movie. Butters is annoying and adds nothing to the plot. I'd advise you to skip it.
It really seem to be a true ending compared to numerous other film series that go on forever and it is nice to see everyone in the ensemble and crew joining up for one final time, but an annoying Chris Rock and the downright theft of the dentist interrogation scene from Peter Sellers are unforgiveable and the plot is sadly mostly on auto-pilot.