Character creation is an important part of the experience in Biomutant, as the decisions made here will impact how the rest of the game is played. Among the many choices players must make including breed and appearance is the character's innate resistances. Players have 25 points of resistance which they can spread out between the four different options, those being heat, cold, radioactivity, and biohazard. There isn't much explanation of what these all do, and new players have no way of knowing which of these resistances will be more useful in the long run. Thankfully, the decision isn't actually all that important.
In Biomutant, players will come across hazardous areas that are "infected" with one of the four problems listed above. While resistances may affect the amount of damage players take from enemies using that element, their primary use is to allow the player to enter these hazardous areas and remain in them for longer.
The first reason why these resistances don't matter too much is that players will find gear that increases their resistances anyway. The decision made at the beginning here will not likely ever stop the player from proceeding as they should have gear to help them. Another important thing to note is that these hazardous areas aren't very prevalent early on in the game. That said, if players do want a hint as to what they should focus on first, heat and radioactivity are safe bets to start with.
The biggest reason players shouldn't worry too much about this choice is because players can always upgrade their innate resistances as they play the game. Open the radial menu and navigate over to the character menu. In the mutations tab, players can spend their Bio Points to increase any of their resistances. With each increase purchased, the player's innate resistance to that hazard will increase by 10%. In order to get more Bio Points, players will need to either kill Bio Creeps for a rate of about one Bio Point per kill (more for tougher enemies) or find Bioblob Containers.
Ultimately, players should simply choose the resistances that they feel make the most sense for their character or that seem the most useful to them. As previously mentioned, some players have reported that heat and radioactivity resistance has helped them more, but others prefer to dump into biohazard since these areas are where players can farm Bio Points the easiest. There's also the option of splitting the points up evenly to take a more balanced approach.
Biomutant is available now on PC, PS4, and Xbox One.