Like any other boss in Beyond, he also awards the user 50,000 Ryo.
Orochimaru stands in the middle of a rocky platform near his hideout, if he is attacked he will relentlessly assault you, most commonly performing an infinite combo until the one who attacked him is dead. He has a habit of summoning snakes repeatedly throughout the fight, overwhelming anyone unfortunate enough to get near.
Strategy 1 (Team)
Because fighting him alone without the right equipment is nigh impossible, it is best done with only two people if it is to be done in a group as more than two can make the fight hectic and confusing without communication. One person starts by attacking with Taijutsu, up until they themselves get attacked by Orochimaru, while they are being attacked the second goes in and attacks. If done right this should cycle back and forth until Orochimaru is defeated.
Strategy 2 (Solo)
This strategy requires Hawk Summoning, Toad Summoning,Shadow Clone Jutsu, and Snake Summoning, Because Orochimaru has no Jutsus and would much rather assault you with melee and snakes, this makes it easy to cheese him with summons of your own. First start with Hawk, wait a few seconds then deploy a Shadow Clone alongside a Toad, then do the same with a Snake. Orochimaru will be so focused on your summons he will not go for you and because he can't shake them off without jutsus they have free reign to beat him down. If done right you will have then beaten him without taking a single hit.
Strategy 3 (Solo)
[REQUIRES ICE + SHADOW] Start equipping: Ice Defense, Ice Transpierce, and Shadow Stitching. First start off with Ice Defense, regenerate, Ice Transpierce, regenerate, and then finish off with Shadow Stitching. Rinse and repeat. If you're trapped and Orochimaru is about to attack, use substitution and shadow clone as soon as possible. Any thing like summonings, modes, companions, Dojutsus/Other KG will benefit.
Strategy 4 (Solo)
This strategy is similar to Strategy 2, but it doesn't really require summons. Only your good ol' fists. Orochimaru has no ability to move and gets stunned every time you hit him, so what you should do is just spam left click (Taijutsu) on him. Make sure you have a LOT of stamina, use Gaara's Gourd for example for the stamina boost. Once you run out of stamina, spawn a clone to take care of him while your stamina is regenerating. Once it is done, you can fight him again. Repeat this process until he is defeated. This method is one of the quickest ways to do it, because it's all close and personal.
Strategy 5 (Solo)
This strategy requires the use of other people. When Orochimaru spawns, alert the server of this via the chat, i.e. 'OMG, OROCHIMARU HAS SPAWNED, GUYS, LET'S TEAM UP!' Hopefully once you have done that, people will come to the fight and attack Orochimaru for you. You just need to sit back by the area where the 'Curse Mark Sub-Jutsu' spawns. Wait for the helpful people to kill Orochimaru, and claim the fruit of your efforts. Granted, the server will hate you for it, but, let's be honest, you have the curse mark - who cares?
Strategy 6 (Solo)
This strategy is very similar to Strategy 4, except it is more efficient. Instead of just using fists to spam Taijutsu on the boss, you can use one or more of these: Custom Susano'o, Iron Release, or Primary Lotus. If you can use at least two, it is even better. Activate Custom Susano'o First Form, Iron Fist, and/or equip Primary Lotus. Now you can spam left click (and Primary Lotus) on the boss (see Strategy 4). This strategy is also good for farming experience points and ryo.