Ricardo Fuller's first-half strike had put the Addicks ahead but two-goals in four minutes from the Championship's top-scorer left Powell's side eight points above the drop zone.
And after seeing his side dominate the opening half only to come away nothing, Powell was left rueing missed opportunities.
"I would say that in the first half and even the first hour, it was some of the best stuff we've played," he said.
"But of course, you need to take your chances when they come and we needed to take more than the one we got because we knew there would be a response from Palace.
"Obviously, somebody like Murray, who has been scoring goals all season, he eventually got his chances and he took them.
"It's tough to take because it could be quite easy to forget about how well we played in that first 60 minutes.
"It was a proper local derby with chances at both ends.
"It's just a body blow we didn't come out on top."