The only detail I can remember is that there is an agency woman (american), possibly redhead, who is sent to infiltrate an enemy gang (in africa i believe) by seducing the leader. she is later discovered, killed with a machete and buried in a pool outside the gangs house. her body is discovered at the end of the film by the agency members.
“The Bank Job” (2008)?
A Jason Statham movie.
It starts and ends similar to what you described.