#Pepe, 47 bytes

REREEeRErEErREeeEeeeeEREEeeREEeereeREEEEeeEReee

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Explanation:

REREEeRE # Push 0,then input (str),then 0 -> (R)
         # The zeroes are pushed to correct the inserting
rEE # Begin loop labelled 0 -> (r)
  rREeeEeeeeE # Push "!" -> (R)
              # r flag inserts it instead of pushing
  REEeeREEee # Move pointer pos 2 steps forward -> (R)
ree # Loop while (R) != 0
REEEEeeE # Remove characters of (R) that are in stack of (r)
         # Removes the 0 in (R)
Reee # Output (R)

Pepe, 47 bytes

REREEeRErEErREeeEeeeeEREEeeREEeereeREEEEeeEReee

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Explanation:

REREEeRE # Push 0,then input (str),then 0 -> (R)
         # The zeroes are pushed to correct the inserting
rEE # Begin loop labelled 0 -> (r)
  rREeeEeeeeE # Push "!" -> (R)
              # r flag inserts it instead of pushing
  REEeeREEee # Move pointer pos 2 steps forward -> (R)
ree # Loop while (R) != 0
REEEEeeE # Remove characters of (R) that are in stack of (r)
         # Removes the 0 in (R)
Reee # Output (R)

#Pepe, 47 bytes

REREEeRErEErREeeEeeeeEREEeeREEeereeREEEEeeEReee

Try it online!

#Pepe, 47 bytes

REREEeRErEErREeeEeeeeEREEeeREEeereeREEEEeeEReee

Try it online!

Explanation:

REREEeRE # Push 0,then input (str),then 0 -> (R)
         # The zeroes are pushed to correct the inserting
rEE # Begin loop labelled 0 -> (r)
  rREeeEeeeeE # Push "!" -> (R)
              # r flag inserts it instead of pushing
  REEeeREEee # Move pointer pos 2 steps forward -> (R)
ree # Loop while (R) != 0
REEEEeeE # Remove characters of (R) that are in stack of (r)
         # Removes the 0 in (R)
Reee # Output (R)