The berserkir were not what we think they were, according to Viking and Old Norse scholar Roderick Dale. Snorri Sturluson's translation "bare-shirt/armor," suggesting a nakedness and recklessness is now not favored. It is more likely to be "bear shirt/armor." They were unlikely to be the out-of-control warriors of fantasy, and more likely became the protectors of order, the bodyguard of the king, and then the protector of the helpless. The champions, in the old sense. There was a ceremonial aspect in preparing for combat that may have functioned rather like Maori Haka. Even when knowing it's a performance, the disquieting thought "some of those dudes look actually crazy" does creep in.There is reference to Christian berserkers, something of a precursor to the idea of the Christian Knight, turning his prowess to the service of women, children, and the poor. The references to this being an out-of-control group, as dangerous tend to be later.
Yet wolves were mentioned far more frequently. The relation of wolf-ness to warriors is actually much stronger, and bears were subsidiary. There is an idea that there must have been wild-boar warriors as well - we like such things in triplet - but the evidence for this is meager.
Wolves, then. That is fascinating in terms of David Anthony's book in progress The Dogs of War which I keep hearing excitement about but is only a single paper at the moment. Still the archaeological incident the paper is about is quite something, of dogs - likely old pet dogs - cut into pieces and then eaten by boys in a coming-of-age ceremony, and it is David Anthony, author of The Horse, The Wheel, and Language. I have heard Anthony discussing the overall idea of the centrality of dogs and wolves to warfare in the many Indo-European and even specifically Yamnayan cultures. The association of dogs, wolves, and war is still strong in many of the descended cultures.
Razib's series on wolves and humans on the Eurasian Steppe The Wolf at History's Door and Casting Out the Wolf in our Midst are recommended. I don't know how much non-subscribers have access to, but his usual practice is to give you at least a few paragraphs.
Those behind the Hajnal Line may have gradually become less violent within their own societies* and their descendants less murderous now, but this is on top of a part of one of the most violent groups in history. We can tell by the genetics that ten women reproduced for every man through those times, meaning that ten was the average number of women impregnated by the successful males, who likely enslaved or simply killed the male opponents they encountered. Whether that was abduction or rape and abandonment is unclear. If you are looking for ancestors to hate, it might be best to skip the colonialists and move straight to the coming-of-age cohorts of the Yamnaya who subdued and overran Europe and half of Asia in the Bronze Age. Their societies tolerated and even encouraged it because the violence was directed ever-outwards, and thus more land and treasure for us all! Later descendants channeling that violence in milder form still carried the ceremonies.
*However, because of their related ability for broader cooperation than other societies, they have been quite good at violence directed at enemies.