Trail Of Corpses has to be, by far, one of the most tedious trophies/achievements to unlock.

Having to kill 53,596 infected would normally take a very long time. Days or possibly even weeks for some; well here's a tip on how to obtain that trophy in less than 2.5 hours.

When you unlock the event "Rolling Thunder" you gain access to a Thermobaric Tank with infinite missiles, and endless hordes of infected enemies. The event gives you exactly 2 minutes; which is more than enough time to rack up over 1,000 infected kills, using the Thermobaric Tank's stupidly overpowered missiles.

When you start the event, go straight onto the road adjacent to the starting position and drive backwards. Fire your missiles repeatedly at the enemies in front of you (and around you) for quick and easy kills.

Keep repeating this event over and over. In less than 2.5 hours, you should have well over the 53,596 infected kills needed for the "Trail Of Corpses" trophy/achievement.

this tip had few steps:
1)mark RAINING FIRE event (EVENTS>Kill>6th from top)
2)go find the event
3)start the event
4)you got 2 minutes helicopter with infinite missles
5)kill the nearst Base or Hive (or both that will be better) with homing missles to do the most damage (do it as fast as you can) and there you go 50k-300k ep per 2 minutes if you do it well

When you are fighting the Supreme Hunter on the last story mission, you are most strong with the Blade w/Armor. But an easy way to to this tip is grab a missle launcher soldier. He should be on the far sides of the ship. Grab the launcher and shoot at the Supreme Hunter. If he isn't stunned yet one or two slices from the Blade will help. Once it is stunned and is ready to be grabbed, change to Musclemass and then grab him. All of these punches count as if punches from regular form. But if you change to Musclemass the punches will be stronger, since that's what Musclemass does. This helps alot. It will take a great chunk out of its health.

When jumping great distances, building to building in waypoint events you can often land from a high position to perhaps ground level or a much shorter building - this makes your character pause as he hits the ground with a slam (doing some mild damage on the area around it). This little animation stops you dead in your tracks and can lose you valuable seconds if you're trying for Platinum Medal on events.

To avoid this halting animation, just before you hit the floor activate the air glide move in the direction of the next waypoint, then right after the glide, drop down and land with an airdash to the ground - If done at the right height and timing, your character will hit the ground sprinting forward at full speed rather than stopping and from here you can continue to cover more ground with giant leaps.

Easy mode:
Elizabeth Green:
1) acquire Air-Ground spike upgrade and Blade air slice (reccomand to get max critical mass upgrade to)
2)go on 1 of the buildings and consume some hunters
3) jump from the buildings towards elizabeth and use the air-Ground spikes
4)repet till its stunned and then use max charged Blade Air slice twice and go on one of the buildings (done use 3 times cuz it might fail you cuz she usually get up and use devestator after the 2nd blade air slice)
5)repet until she dies Good luck! =]
Supereme hunter:
1)Acquire needed: Blade Air slice and the Tendril Barrage Devastator is nearly all you need (recommanded to get max critical mass upgrade and max health upgrade)
2)use the Tendril Barrage Devastator to stun him and then grab him and attack him fast
3) use the blades air slice attack many times untill he uses his devastator (if he throw something on you catch and throw it back)
4)when he uses his Devastator exectly in the moment that the tendrils come back to his body you need to hit them with the air blade slice
5)repat untill he dies
extra tip for both: use air dash to avoid the range attacks and the devastators!
normal+hard mode:
Same as easy just be more carful (MUCH MORE carful)

To watch the transformation cutscene instead of just tapping the directional button for the transformation, hold it in and there will be a short cutscene of Alex transforming.