Ok, I'm missing:
You'll Feel a Little Prick (Assist in killing 3 enemies with a single ÜberCharge on a Scout.) Advices?
Medical Breakthrough (Assist in destroying 5 enemy Engineer buildings with a single ÜberCharge on a Demoman.) Advices?
Doctor Assisted Homicide (Assist in killing 20 nemeses.) No problem here 14/20.
Chief of Staff (Accumulate 1 million total heal points.) No problem here, it takes some time.
Blast Assist (Assist in exploding 5 enemies with a single ÜberCharge on a Soldier.) Advices?
You'll Feel a Little Prick (Assist in killing 3 enemies with a single ÜberCharge on a Scout.) Advices?
Medical Breakthrough (Assist in destroying 5 enemy Engineer buildings with a single ÜberCharge on a Demoman.) Advices?
Doctor Assisted Homicide (Assist in killing 20 nemeses.) No problem here 14/20.
Chief of Staff (Accumulate 1 million total heal points.) No problem here, it takes some time.
Blast Assist (Assist in exploding 5 enemies with a single ÜberCharge on a Soldier.) Advices?