SO ABOUT THAT DIAMOND CARD.
Basically, with this kind of status effect, being needy for Prussia involves a horribly insistent need to please whoever he's around. This basically means he will get upset when he thinks that he's disappointing/angering/annoying/bothering/boring a person. He is actually really insecure, primarily because this kind of status effect amplifies a lot of closeted issues and personality traits and will be confused and flustered and nervous a lot of the time until someone points him a direction, which he will jump at the chance to follow because maybe they'll appreciate it and love and attention and tailwag tailwag loooove meeeee.
Prussia himself is a nation who was founded as an order of knights--i.e. people who worked under the rule of a greater entitiy, in this case the Pope and the Emporer. Prussia has a lot of that to his personality, a need to belong to someone or something--an ideal or a person or even another country. This is largely why he clings to people he grows attach to and also why he doesn't let a lot of people too close. It is a major weakness, in his eyes, having to depend on others--a viewpoint history has taught him to be true again and again as he's experienced moments of helplessness when vital decisions are left up to others not himself.
As a kingdom, Prussia found himself with a lot of power and a more dominant mindset. This is around the time where he shut away that kind of subservant nature--except, of course, while he may never quite admit it, he did build up the German Empire because he was hoping not only to leave something of himself should anything happen to him (because countries like him with no true history and essentially sythnesized through the conquering of others, he would live a pretty active and violent, but short lifetime--something of course he will outwardly deny like no tomorrow) as well as to build up an empire strong enough that he would be willing to follow them. Because that's what Prussia was, how he was founded.
And it's these things the status effect amplifies--removing a lot of the masks of determined stubbornness and hard-headed dominance. It's a very very vulnerable side to Prussia, however, because the card makes him need the constant reassurance that yes, he's wanted, yes, he's needed, yes, he's doing what the person he's near wants, and yes, they are pleased with the results.
For most people, he'll just go along with what they ask of him and get nervous and fidgety when they try to have him do something for himself because WHAT IF HE DOES IT WRONG AND THEY GET UPSET FAILURE AND NOOOOO LOOOOOVE. Which is horribly demoralizing, but he can get over as soon as he has someone else giving him hugs and pets and acceptance.
There are, however, a select few people with which Prussia will drive himself crazy trying to do right by because he CARES SO DAMN MUCH ABOUT THEM and HAS TOTALLY FUCKED UP WITH THEM MORE THAN ONCE. In this case, Prussia will be at his clingiest--constantly seeking approval and acceptance and love, mostly. This might include people such as Germany and Ikki. It miiiight even extend to people like Zexion, Deb, and Itachi. It really depends. With Germany, though? It'll be the worst, because he will literally be clinging to his brother like a lifeline and uh. Y-yes. That will be a beautiful thread.
When this is all over, though? Prussia will be ABSOLUTELY MORTIFIED. He will likely not leave his room for a couple of days. Because Prussia as he is HATES and LOATHES showing weaknesses and this status effect has a way of displaying all of his insecurities as well as some made-up ones thanks to camp. Haha...