Letters, Get Moving! Pt. 2

CJam, 41 38 bytes

lee_S+W%\{Xa-X1='`-/(Xa+\L*+}fX1>W%1f=

Test it here.

Python 3, 78 bytes.

Saved 2 bytes thanks to orlp.
Saved 7 bytes thanks to DSM.

x=input()
y=[]
for z in x:m=max(len(x)-ord(z)+96,0);y[m:m]=z
print(''.join(y))

Builds the word as a list then joins it.

Python 2, 86 bytes

a=input();k=list(a)
for i in a:k.remove(i);k.insert(ord(i)-97,i)
print"".join(k)[::-1]

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Python 3, 88 bytes

a=input();k=list(a)
for i in a:k.remove(i);k.insert(ord(i)-97,i)
print("".join(k)[::-1])

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Examples

Python 2:

$ python2 test.py
"flower"
rweolf

Python 3:

$ python3 test.py
flower
rweolf