Here is our scenario.

Currently, when pinging any interface on Router2 with 50 packets 100bytes each from Router1, the result is 100%. Change it so the success rate is always 96%.

Assuming FastEthernet Interfaces.

Router1 - Router2

—Configure control plane policing on Router2

access-list 110 permit icmp host [Router1] host [Router2] echo

class-map ICMP

match access-group 110

policy-map ICMP

class ICMP

police rate 80 pps

control-plane

service-policy input ICMP

Then from Router1 do a ping:

ping 2.2.2.2 size 100 repeat 50

Sending 50, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!.!!
Success rate is 96 percent (48/50), round-trip min/avg/max = 1/3/9 ms

Enjoy!