Mugen no Juunin: Immortal

Similar premise of a swordsman who has to kill people/things to fix a checkered past. They are both accompanied by a younger person on their journey. Both series take place in Feudal Japan, with some aspect inspired by Japanese mythology with Immortal being more grounded. The two series are also fairly violent with many fight scenes. The main difference is in tone, where Dororo is overall more light-hearted while Immortal is a 100% seinen show. 

Both are gritty, mature stories of revenge set in historical Japan. They pull no punches unafraid to show the darker side of humanity.  

Both happen during the Edo Period of Japan. Both are about the journey of the characters and how they encounter different enemies. Samurai Champloo is funny, while Mugen no Juunin has a more serious theme, but I think that if you enjoy one of these you woul enjoy the other. 

bloody no holds barred action about a lone samurai/ninja and a female protagonist  

Very cool and gore-y fight scenes. Both plots are very similar and share the "vengeance" theme. 

Both Are Brutally Violent, Unrelenting and Action Packed. and Certainly Not for the Faint of Heart. With Badass Protagonists.  

Both Sword of the stranger and Blade of the immortal (2019) are similar for sword fighting anime. In two series, there is a lot of blood , you fight exciting and an interesting history 

Hellsing and Blade of the Immortal are similar in certain aspects as in aspects from their characters, as they both start with a male and female duo working together, with both Manji and Alucard expressing patience for their "disciples" (Rin and Seras respectively) as they teach them to reach their full potential while being the most powerful out of the two, however even with how they are basically immortal there's a difference with their powers, the former can fully regenerate and has other powers (sharp perception, aestivation, hemokinesis, shapeshifting, unleash familiars, etc.) while the latter needs to attach limbs back when cut and is generally more vulnerable to attacks (having more ways to be killed shown than Alucard). In a way, both are eager to fight "worthy adversaries" which vary from personalities but many do wicked and foul actions, not like they are much better as they hold some level of moral grayness by how brutal and cruel they can be. Both series have great fights and animation with some nightmarish and disturbing imagery to accompany it (lots of gore) and while Blade of the Immortal is about vengeance it's also about fighting an enemy organization/s like Hellsing, which can turn into an engaging battle with many players (Millenium and Iscariot for Hellsing, Itto-ryu and Mugai-ryu for Blade of the Immortal). read more 

-Two traveling companions in a Samurai era. -Main male characters are immortal in their own way; Sugimoto can fight his way through everything basically without dying while Mugen is indeed immortal and his wounds are instantly healed. -Both anime have deep and amazing story and characters -Animation is decent to very good as well. 

Both are samurai stories for a mature audience. Both have mixed other elements into the historical content that make the events in the story seem heavier or lighter. I liked the touch of sophisticatedness of both, but there are also cool flights and characters and people that are more into these parts will also like both anime. Art is also good in both. 

Young girl witnesses murder of her family, swears revenge. Both anime are quite violent and take place in similar setting of past Japan, although visibly different era, yet still gives off similar vibe. 

Period setting series with mature themes and a tone reminiscent of the Japanese golden age of film samurai movies. The Immortal is a little more fantastical but I imagine interests in these series will overlap for most people.