φοιτητοπατέρας

[pontios]

Δες τους ορισμούς από τα λεξικά στο #1: έχει αρνητικό φορτίο η λέξη (ειρωνικό, κακόσημο, υποτιμητικό). Επομένως, αποκλείεται κάθε απόδοση με θετική σημασία.

Fair point, nickel.

Student union campaigner/activist - cougr mentioned activist earlier. Activist has a negative tinge to it (could be seen as a troublemaker?), but there's nothing "paternal" about it (and that's why I thought "mentor" might help in my earlier post).

What about "boss" instead of "leader"? The term "leader" evokes more positivity than does "boss".
Student union boss/chief or student party boss. "Boss" has some negative connotations, especially in association with "union or party". Also, a boss is somewhat "paternal" (there's paternal transference at some level), but in a controlling/domineering/pushy way?