Plebian: Dynamic duos are troublesome because they have good teamwork and if either one is in trouble, the other one will come help him.
Big Brain Villains: Dynamic duos are convenient because you just have to take one down to ruin their core strategy, and if you put one in peril, the other one has to help him.
Also, "Grimm is a lot more vigorous at night."
( ͡° ͜ʖ ͡°)