Semi duality is the relationship where the other person leads with your dual-seeking, but doesn’t match in creative and mobilizing function. For an LIE/ENTJ, the semi dual would be an EII/INFP. This is, just as many other ones, an ITR that is good, but far from perfect, without problems. For rational types, Keirsey described this as the optimal relation.
The biggest strength in this relationship lies in how it in many ways is similar to duality. The leading function is the other person’s dual-seeking one, and vice versa. What we seek, they give, and what we live, they seek.
However, semi duality has huge drawbacks as well. First, it doesn’t help us in any way with our mobilizing function. Rather, it leaves that to itself, which makes us want to provide it ourselves. This usually turns out badly however. The bigger problem, however, is that they doesn’t cover our point of least resistance. They are unable to cover those aspects for us, and, even worse, it’s their mobilizing function. They want to flex their muscles, which annoys us to no end.
All in all however, even though the downsides might seem greater, the match between leading and dual-seeking function has a huge impact, and makes this ITR positive in general.