When you know you will be facing a Chimera (i.e. only in the hunting missions) take either explosive or sniper weaponry to try and "one shot" the Chimera.
In Trapper's Chimera hunting quest the easiest way to kill the Chimera is hide under the pipes nearby. The chimera is limited to leap attacks only, so this unconventional tactic of just hiding under some pipes works well. Alternatively, you can arrive at its hunting grounds just before nightfall and climb the nearby watertowers. From this vantage point the Chimera will not be able to reach you, however it is likely to take cover behind the ventilation building if you do not kill it quickly so using either an RPG-7 or sniper rifle is advisable.
If you are very conservative of your ammo, you can sprint up the the Chimera, and make a quick stab in the face, usually resulting in a kill.
If you have a functioning Gauss Rifle, it can kill the Chimera in one headshot. Although when shooting a boar, sometimes two shots are needed when shooting at strong points.