hey guys sorry for late explanation for my riddle
@Akash thanks for conveying my answer to everybody and continued the thread...
guys i'm sorry i was busy last week because dealing with some family issue
Here the answer
ANS. LOVE
I'm the most powerful things by you
in the whole UniverseLove is a deep, powerful and ineffable emotions of attachments to, and affection for another being or beings in the whole universe
Even the trace i leave behind
can turn a Dark Lord's Curse
Lily's love for her son Harry protected him against Lord Voldemort. he became the only known person in history of wizarding world to survive the killing curse because of the power of her loving sacrifice, the killing curse rebounded on Voldemort and destroyed his power...the trace of love for mother to her son protected harry over the years..
The mere facsimile of me
wreaks havoc in a school
Ron and hermione began in the battle one of the most powerful relationships in wizardkind. this is the love for love ones and each other which united every students (even former) and teacher of Hogwarts to fight against lord Voldemort leading to Battle of Hogwarts.
I made a hero out of Snape
Severus Snape's love of Lily Evans pushed him to join the Order of the Phoenix. even though he hated James potter and worked as double agent to protect harry and supported Dumbledore against Voldemort
made Albus play the Fool
Dumbledore trusted Gellert Grindelwald because he was in love with him though Grindelwald betrayed him and this lead violent duel between them... Dumbledore regretted his relationship with Grindelwald later in life.
Invisible, My face is seen
in child a Man or Woman
Self Explanatory, love has no face, its hide in heart of us...
If you try to live without me
you'll end up less than human
Self Explanatory nobody can live without love everybody needs love of someone neither its parents, children, spouse, siblings or friends...if you live without love like Voldemort you hardly called yourself a human.