The following describes the process of achieving victory on the coop brutal scenario. This is not an optimized guide accounting for most disease types to aviod the farm time possibly needed to acquire them if possible. Due to the nature of Co-op, screenshots will not be provided considering the game cannot be paused by one player.

One of the major obstacles to be overcome duting this scenario is the extremely fast cure progression after a plague is discovered and prioritized. Even with max infectivity, high lethality and cure resist, the cure rate at max is nearly impossible to plow through. In order to overcome this, one of the plagues will act as a sacrificial goat in which it would be spotted first and then cured first while a slower and more resilient plague is able to work in the background and then follow up in order to wipe out humanity.

For a translated Russian version of this guide by Akiro if it's your first language go to this link:
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1144951994

Thanks again to you for volunteering your time to do this.

The following guide will provide instructions for a player who would take the role of the main killing agent as well as what is to be called a "sacrifical goat" The killing agent is designed to have a slow start so that not only is it harder to detect, but it also gains a bonus of becoming a more generally infectious plague as a result. The goat plague however is designed to be very infectious in its starting zone but not necesarilly much farther than that. The gene setups are generally as follows, but flexibility is allowed given a user's playstyle. The following uses Bacteria not only because it's the best all around plague, but also it's easier to farm for genes on casual than it is to try to get a particular disease type. Be mindful that the agent is much more gene dependent than the goat, so if one player has less genes than the other, but still want to complete the achievement, they should play as the goat.

The following setups are for as given set of starting countries that will be described in the gude. If other starting countries are used, then these genes can e tailorred to the user's playstyle.

Agent:

Bacteria

• Xerophobe
  
• Pharmaphile
  
• Thermophobe/Urbophobe

Goat:

Bacteria

• Benign Infection
  
• Xerophobe
  
• Innocent Infection

Starting country: Saudi Arabia

The general strategy is to lie dormant with a very long ramp up time while your partner is making the world cure them and they're flying you to islands that you couldn't normally reach with air and land travel. The initial severity is high enough to gather sufficient dna for the late game, and since the cure and environmental resistance are the major issues in this mode, you need enough cure resistance to handle labs as well as enough resistances to be able to spread effectively when the world is distracted.

At the very start of the game, get Air 1 & 2 followed by Rash and Abscesses, then Bird 1 and 2. This provides not only a means of reliably spreading to a variety of countries through air travel with land spread to aid in getting to every country reliably, but also enough severity to get 2 dna per red bubble. Then get cold and drug resistance 1 while the world is getting distracted by the goat plague. Follow this up with drug 2 and cold 2. Once cure progress begins to ramp up, steal infectivity and get preshuffle. Once Saudi Arabia is nearly fully infected, follow it up with dust 1, blood 1 and livestock 1 and Genetic Hardening 1 as well as 2 if you have spare DNA.

When the goat plague is mostly or fully cured, and the attention is now on you, steal DNA complexity, and evolve skin lesions, necrosis and total organ failure to kill the people curing you, break down governments and destroy cure labs. Steal lethality and evolve rodent 1 to ensure the remains of china are destroyed. If any regions that struggle to get infected such as central asia or some african or middle eastern country, get dust 2 or blood 2 to counter this. If cure progress is too fast, buy whatever cure resistance options are at your disposal by rushing to coma and then reshuffling to ensure you get the most out of them as a lower cure rate grants a more effective reshuffle.

Starting Country: China

The general strategy is to buy your partner enough time to be able to spread by infecting large population centers and distracting the world. In addition, the ability to boost the main killing plague's ability through infectivity and cure resistance as well as travel greatly aid in improving the reliability of your partner's plague. While this role does seem silple at first, lining up the timing between your partners spread as your time being cured to match where your partner is exponentially growing just as you're nearing being cured is key to reliably pulling off this strategy.

First, evolve rodent 1 and reshuffle preparation. At this point, start ramping up symptons in the inflammation tree and gain a path to a slight level of lethality. Once China becomes fully infected, gift your partner infectivity and evolve heat resistance 1, droplets 1 and insomnia to buy your parner more time. Then go for unexpected flight and start flying your partner to as many islands as possible wihout airports. Balance this with evolving paranoia for cure resitance.

Once your cure progress has reached 90 percent. evolve genetic sacrifice and let yourself be cured. If all other islands are cured, go for the infectivity active ability and boost it in primarilly poor and arid countries as well as china due to the low base urban resistance of all non-native plagues.

The following is a run in which this stategy was implemented succesfully. There will be 2 videos, one from the perspecive of the agent and the goat respectively.

Agent's Perspective:

Goat's Perspective:

Credit to Modern Bolt for the gameplay

Overall, the relability of this plague is dependent on coordination between yourself and your partner to overcome the oddities of the coop plague conditions. Communicate where dna will be invested and provide input as to how you would wish to go forward. Best of luck in performing this, and let me know as far as any relevant feedback or specifics that would aid in this strategy.