That's a tricky one because 'Vinland Saga' shifts so drastically after the first major arc. If you're looking for the combo of visceral combat and character depth, I'd point you toward 'Kingdom'. It's got the sprawling historical war drama down, with insane battlefield tactics that make you hold your breath. The character growth, especially for the young protagonist Xin, feels earned over hundreds of chapters – he starts as a brash kid and you slowly watch the weight of leadership settle on him. The political machinations are there too, just less philosophical than 'Vinland Saga' and more straight-up strategic.
For something with a darker, more psychological edge, 'Blade of the Immortal' is an older title that fits. The fights are brutal and technical, but the core is really about a cursed man seeking redemption through violence, which echoes Thorfinn's journey in a way. The art is stunningly detailed in its grotesqueness. It doesn't have the same clear 'prologue' and 'farm arc' separation, though; the moral questioning is baked into every conflict from the start.
I'd be cautious about 'Berserk' as a recommendation even though it gets mentioned a lot. The early Golden Age arc has that brotherhood-turned-betrayal drama, and Guts is profoundly deep, but the tone and content are far more relentlessly grimdark. It lacks that central, transformative pivot toward pacifism that defines later 'Vinland Saga', so your satisfaction depends entirely on which phase of Yukimura's story you're craving more.