Here is how to get a 4 star Global Ranking at the End of all Levels in Solo mode, i take no credit for this as it was taken from http://www.ps4trophiesgaming.com/blue-estate-2/blue-estate-t...
Here are the main things you need to Aim for when going for the 4 stars in each level:
You need to get a 4 star global rank on each level in the game. There are 9 categories that you are ranked on each time you play a level and each of those 9 have their own individual 4 star ranking. To get an overall global rank of 4 stars, you will need to get 4 stars on 6 or more of the individual categories. They are:
Average Enemy Lifespan
Warning Sign Kills
Hidden Collectible Objects
HOWEVER you can Unlock the Achievement by only getting 4 stars with Gestures, Melee Attacks, Warning Sign Kills, Nutshots, and Collectibles. thanks to The SCHWARTZ 00 for Mentioning that too me :)
Your total time and total deaths do not factor into this at all. Try to focus on Quick Gestures, Melee attacks, Nutshots and collectibles. These four categories are fairly easy to get 4 stars on if you devote time to them.
Shoot all collectibles.
QUICK GESTURES – These are simple to get 4 stars on. A quick gesture is recorded when you make a correct touchpad gesture immediately after given the on screen prompt. When properly executed, you will see “speed demon +5000? on your screen. Most gestures counts including hair swipes, Chihuahua leg shake offs, health and ammo pick ups, opening doors, jumping, climbing, etc. Melee attack gesture prompts do not count. To easily get a quick gestures, make fast circular movements moments before approaching a QTE event. For example, you see ammo at the end of a hall, before reaching it, start spamming a quick circle motion on the touchpad and you will get a quick gesture. If you’re unsure of QTE locations, just make the quick circular motion anytime you aren’t actively engaged in battle.
NUTSHOTS – Once a level started, I focused on killing 10-15 enemies with a nutshot and then focused exclusively on headshots only. Try to be efficient because each nutshot is one less headshot and you are ranked on both. If the enemy is wearing body armor, you may want to just go for the headshot instead or risk losing your combo.
MELEE ATTACKS – There are only a certain number of melee attack opportunities in each level. When you have a chance for one, don’t shoot the enemy. Let him come to you and you’ll need swipe the touchpad to kill him. You’ll know which enemies are going to be close enough for a melee attack they are carrying a melee weapon instead of a gun. Again, be careful not to shot them first. You’ll be alright if you accidentally shoot a couple.
Those are the fairly easy ones that you have the most control over. Now you just need to get 4 star ranks on 2 of the remaining categories.
BEST COMBO – You’ll need to rack up a massive combo to get 4 stars. Think 200+. There is a circle timer on the top of your screen with your current combo multiplier. When the white outline timer is empty, you’ll break your current combo and start new. A combo is built by killing enemies prior to the white outline being empty. You’ll keep the combo up as long as you quickly take out each enemy. The combo killer is running out of ammo. Make sure you reload prior to each encounter and if you have to reload during battle, do it immediately after killing someone or switch weapons instead. There are opportunities that Hold LT to get into Cover, When in cover, the timer is paused so at this point you can reload or even switch weapons.
Average Enemy Lifespan – This is one of the tougher categories This is how long the average enemy is on screen. To reduce this, you’ll have to be very quick and use environmental explosive objects to kill multiple enemies at a time. I found it best to just ignore this.
SHOOTING ACCURACY – Really easy since the enemies don’t move around much. This will most likely always be a 4 star rank if you’re taking careful headshots with a single bullet. Each level has a secondary gun that is much better than the starting pistol so conserving ammo by getting one shot kills will help. With the assault rifle or SMG guns you get, take short tiny bursts and aim for headshots.
HEADSHOTS – After you get your nutshots, you should only be going for headshots the rest of the way with the exception for melee opportunities. All other types of kills will reduce the possibility to getting a 4 star rank on this so I found that using explosions to kill people was counter productive.
Warning Sign Kills – This is when you kill someone when they are about to shoot at you. You know they are about to shoot when you see the yellow circle. Enemies with yellow circles should ALWAYS be killed prior to you shooting at anyone else. You are ranked based on how often you shoot someone with the warning sign. Playing on Normal difficulty will give you more time to shoot them.
Hope this Helps Anyone Out who were wondering how the 4 stars was obtainable.