Among other concepts, Pluto represents control, manipulative and Ascendant represents approach to life, the person itself. When Person 1's Pluto conjuncts Person 2's Ascendant, it could mean that Person 1 hovers over Person 2 and tries to control or manipulate the latter's every action, behaviour, especially when the orb is tight. The controlling could be done in the background, in a overt and hidden manner.
A skilfull use of the energies for Person 2 to get in touch with his/her darker self - to be controlling, manipulative, ruthless, secretive, etc. The traditional view of Ascendant is that it is an angle, which only "receives" energies. But surely you can argue that by receiving Plutonian energy, Person 2 is exposed to such energies and may arouse it within herself, if it's not already the case.
I think it's best for Person 1 to understand the dynamic in the relationship and consciously adjust his/her behaviour, as with most hard Pluto-personal planet aspects in Synastry. For to love someone is to let go of the person, without a need to control the person, regardless of whether you think control is beneficial or even necessary for Person 2. Some believe that love can transcend death (Pluto). If that's the case, let your love for Person 2 transcend your dark self.
Cosmic Insights for an Even Better Life