Does an ascendant in Scorpio have the strongest placement?

One single placement can not determine the strength of an energic influence. In order to see the strength of a particular sign, planet, or house, you would need to synthesize the whole Natal chart. Sorry, this probably isn't what you wanted to hear.

To have Scorpio on the Ascendant is a nice piece of the puzzle, though. The first impression others will get of you is of someone who is somewhat aloof and standoffish. You liven up around others you know and quiet yourself around people you don't. Your mysterious aura will either be attractive or repulsive.

When considering psychological or esoteric astrology, the rising sign is where we look to see how are traits develop and get a glimpse of the type of person we become when we work with both the positive and negative aspects of self.

For a Scorpio Ascendant, we meet someone who has attained power either through influence or manipulation. Someone who's mysteriousness becomes a projection of the insecure who are too intimidated to approach and dispel the mystery. For when they approach, they meet a kind, thoughtful, and empathetic individual whos finds fulfillment in encouraging and supporting others.

Again further insights can be gleaned from a full Natal Chart interpretation, but I did the best I could with the info I had. Hopefully, you find this info beneficial!