This is one of those combinations that is extremely hard to get wrong. Berserkers and fighters both typically want Strength as their primary ability score with Dexterity and Constitution as numbers two and three in the order of priority. The order of the priority of those second two is probably reversed for fighters and berserkers with fighters slightly valuing Dexterity more highly and berserkers valuing Constitution in the same way. Flavor-wise, there’s also a ton of synergy, with it not being much of a stretch at all to imagine a character who has taken levels in both of these classes. And unless the fighter levels are focused on ranged combat in a specialized capacity, this character will probably play about the same regardless of the precise mix of levels: get in close with a high AC and high hit points, and pound on targets with a big melee weapon. A higher focus on berserker levels will give you a character that is more instinctive and ferocious in combat, but with some serious training under their belt. A stronger focus on fighter levels will give you more professionalism and technique, but also the ability to “overclock” when the situation demands it. [[Synergy Feats for Multiclassers#Berserker w/ Fighter|Berserker-Fighter chains and ideas]]