Once you receive the Bear Might power you are given the tutorial of how it works. At this point you are attacked by about 30 Washington clones. Just keep clustering them up, and using Bear Might. If you are trying to Full Sync the memory then reloading the checkpoint keeps your kills if you get hit.
I got it this way by accident as a random Washington would punch me, and I just reloaded last checkpoint. Took a max of 2 minutes to do.