The estimated time for 100% achievements on Serious Sam 4 is about 11-15 hours. The achievements are also quite easy and everything can be done on the lowest difficulty on the game "Tourist".

Here are some F.A.Q.:

• Is there more than one playthrough required? No.
  
• Are there any Multiplayer/Online achievements? No.
  
• Are there any missable achievements? No. Every achievement can be done at any time.
  
• Are there any bugged achievements? No.
  
• How many hours do I need to get 100%? 11-15 hours.
  
• How hard is it to get 100%? 2/10. (1=Ultra Easy and 10=Ultra hard)

Finish chapter 00 called "Man vs Beast". [Short Intro]


Finish chapter 01 called "Death from Above". [Estimated Time: 20 min]


Finish chapter 02 called "Death from Below". [Estimated Time: 20 min]


Finish chapter 03 called "Four Horsemen of the Apocalypse". [Estimated Time: 50 min]


Finish chapter 04 called "Gates of Hell". [Estimated Time: 30 min]


Finish chapter 05 called "The Die Is Cast". [Estimated Time: 40 min]


Finish chapter 06 called "Morituri Te Salutant". [Estimated Time: 25 min]


Finish chapter 07 called "When in Rome". [Estimated Time: 25 min]


Finish chapter 08 called "Machina Ex Deus". [Estimated Time: 25 min]


Finish chapter 09 called "A Breakfast in France". [Estimated Time: 45 min]


Finish chapter 10 called "One for the Road". [Estimated Time: 45 min]


Finish chapter 11 called "Vive la Résistance". [Estimated Time: 45 min]


Finish chapter 12 called "In Carcassonne". [Estimated Time: 45 min]


Finish chapter 13 called "Anathema Unto God". [Estimated Time: 45 min]


Finish chapter 14 called "The Package". [Estimated Time: 15 min]


Finish chapter 15 called "From Earth With Love". [Estimated Time: 60 min]


Finish every chapter on any difficulty. The difficulty levels in Serious Sam 4 are the following:

• Tourist
  
• Easy
  
• Normal
  
• Hard
  
• Serious

or alternatively

Easiest Way: Start chapter 00 - "Man vs Beast", spend the whole magazine (= 1000 bullets) of your Minigun while firing continuously and don't move forward.



Simply kill five enemies while your health is below 10 HP. Please note that the five enemies don't have to be killed in a row.



For the best chances use your double shotgun on groups of beheaded enemies (in particular: Beheaded Bomber, Beheaded Firecracker, Beheaded Rocketeer, Beheaded Kamikaze). It is not hard at all.



For this achievement just simply kill 100 enemies with a headshot. I prefer to use your pistol ("SOP38 Semiautomatic Pistol") on the enemies called Processed Anthropolyp [serioussam.fandom.com] or Octanian Gamma Trooper [serioussam.fandom.com].



The Emetic Anthropolyp [serioussam.fandom.com], commonly referred to as Belcher, is an enemy that appears right in the first chapter "Death from Above". The unique feature of this enemy is that it explodes upon death and causes damage to all enemies within a small radius. To get this achievement just get two Belchers near to each other, weaken them and then kill one of it so that the other one gets killed by the explosion upon death of it. It really isn't that hard.



You can do this right in the first chapter "Death from Above" after getting the double shotgun. Just shoot them in the head when they are close to you.



The Aludran Reptiloid [serioussam.fandom.com] is firstly encountered in the third chapter "Four Horsemen of the Apocalypse". Just kill one of them at any point in your playthrough only using your pistol.



Equip your double shotgun, let a Kleer [serioussam.fandom.com] come close to you and shoot him right in his head. Repeat it 50 times and voilà!



The Time Warp [serioussam.fandom.com] is a gadget which can be found through out several chapters. It is firstly rewarded to you after completing the side objective "Amateur Archeologist" in chapter 03 - "Four Horsemen of the Apocalypse". When deployed, it will generate a large chronon distortion field around you which lasts for 30 seconds. Within this “time bubble”, all hostiles and their projectiles will be dramatically slowed down, while you will continue to move normally. Kill five enemies within these 30 seconds and this achievement is yours.



Propaganda drones can be found in many chapters. Especially in urban areas. They are flying around with a hologram above them and spread propaganda messages with their speakers. Just shoot 10 of them in a single playthrough. Here I will show you how they are look like:




It can be easily done right as you firstly encounter a Witch-Bride of Achriman [serioussam.fandom.com] as the final boss of chapter 04 - "Gates of Hell". In this area is also a full box of C-4. Just weaken her with other weapons and then kill her with C-4.



In chapter 09 - "A Breakfast in France" you have to drive a harvester as part of the main mission. Run over 100 enemies with the harvester and the achievement is yours.



The Psychotropic Grenade is a gadget that can be obtained for the first time as a reward from the side objective "Worm's Armageddon" in chapter 07 - "When in Rome". These grenades will cause a big gas cloud which causes entering enemies to become aggressive towards one another, leading to infighting. Use them on large crowds of enemies. A good and easy place for this is at the very beginning of chapter 08 - "Machina Ex Deus" on the hordes rushing towards you on the bridge.



This achievement is probably the hardest achievement of Serious Sam 4 even though it isn't really hard at all. The Mini-Nuke is a gadget that can be obtained for the first time as a reward from the side objective "♥♥♥♥♥♥ Locked and Hancocked" in chapter 06 - "Morituri Te Salutant". Carry it through until you reach chapter 08 - "Machina Ex Deus". At the big park area run through the whole area and let every single enemy spawn. Now use the Mini-Nuke and you will easily kill enough enemies with it (in particular at least 100). Here is a tutorial video for you:




Near the end of chapter 13 - "Anathema Unto God" you will find the SBC Cannon around with many cannon balls and enemies. Kill them all with your SBC Cannon until the achievement pops up.



Your first skill point (also called S.A.M. - Sirian Artefacts of Might) will be awarded as part of the main story. S.A.M.'s can also be found at secret/hidden places in wooden boxes.




Easiest Way: Finish the game once. Then start (the last) chapter 15 - "From Earth With Love" through the main menu and you will have 10 skill spoints (a.k.a. S.A.M.'s) available. Use them all and the achievement pops up.



For this achievement you have to find/receive at least 3 skill points (also called S.A.M. - Sirian Artefacts of Might) and use them to unlock the skill "Dual Wield Harder" in your skill tree (default key "F" under section "S.A.M.") which allows you to dual wield two-handed weapons such as the double shotgun. Now equip your double shotgun, dual wield it (default key "ALT") and kill 20 enemies.




You will need at least 4 skill points and invest them into the skills "The Bigger They Are" and "The Harder They Fall" so that you can perform melee attacks on medium and large enemies. Melee 11 different enemies with your melee attack skill (default key "E" when they are close). Please note that knife kills doesn't count.

Hopefully I could have helped you all. If you find any mistakes just message me or write it in the comments. Any constructive criticism is desirable!

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Thanks a lot!