barack hussein can't pardon hillary for crimes she has not been charged with. Maybe that is why Comey held off? After barack leaves office, I am sure a Trump appointed FBI Director and a Trump appointed Attorney General, may be able to find just a smidge of intent to commit criminal acts by hillary and bill.
IIRC, the FBI Director is appointed for a ten year term (Unless he resigns, dies or removed from office) Trump may not be able to appoint a new director. (Comey's been FBI director less than 4 years).
However, he can appoint a new AG and Deputy AG's and US Attorney's. So the new ones may be willing to take Hillary to trial.
And yes, Obama can pardon Hillary "for any and all crimes she may or may not have committed." But see
Burdick vs US.
Which may actually be the best way out. Hillary gets to walk, but badly and completely stained and tarnished with the specter of illegality. Yet, the country avoids the entire spectacle of what will be deemed a "political trial", and her being made into a martyr and scapegoat. Which will do nothing but fire up the Democrat base.