Yes, I did it yesterday (30.5.2012). After 3 hours of wiping I killed Belial Inferno Solo with my Demon Hunter and got several achievements. After the kill I killed him again with Macr0s, who already leveled a Monk to lev 60 and geared him for Inferno. We only need 5 more tries for him and it was much more easier then solo. For our team kill I used the same skills and items as I used for my solo kill.
This solo kill was an amazing adventure for me and through this practice I learned really much about my class and improves my playing skills. Of course I must commit that the Demon Hunter is the class which can do this in inferno with really cheap gear compared to other classes.
Inferno Belial Demon Hunter Solo Guide
I won't go into the deep in this guide. I explain how I did it and why. There are of course other and better way to do it and with other gear requirements, but as long the lead to the same success it doesn't matter.
Inferno Belial Build
Hungering Arrow - Devouring Arrow
hatred generator if needed
Elemental Arrow - Nether Tentacles
best damage skill for aoe and single target (can hit a single target more then once)
Smoke Screen - Lingering Fog
Preparation - Backup Plan
Discipline for Smoke Screen
Marked for Death - Mortal Enemy
increase damage and hatred generation in phase 2 and phase 3
Companion - Bat Companion
more damage and hatred generation
movement speed increase for faster positioning
more burst damage, very good with low crit% and high crit damage
I have very cheap gear compared to other classes and what is in the auction house available. My weapon is a magic crossbow with 955,9 dps and critical hit damage increased by 52%.
I concentrate on high dex, high crit damage and ias (increased attack speed) on my gear. (not for Belial but as a general Inferno gear.) If you want spend more money then also consider crit chance and buy pieces like Andariel's Visage with dex, ias and crit. chance. I have following stats.
My quiver has +5 max discipline. This isn't much and if you find a good quiver or chest with other good stats in the ah then buy it for this fight. More discipline helps a lot.
Follower - Templar
The follower is your backup in phase 1 and phase 2. During my tries I bought some cheap equipment for him, because I didn't spent any money for him before and he died to fast.
Two Rings and a amulet with high vitality, maybe a socket.
A shield with high vitality, armor and strength.
A weapon with high vitality, strength and cold damage. The damage itself isn't important.
A Relic with high vitality and strength.
My templar was doing his work with following stats, but sometimes died in the end of phase 2, but this isn't tragic, because you don't really need him in p3 and he will respawn very soon.
Fight against Belial
The fight against Belial has 3 phases. Don't skip the cutscene between the phases. You can skip it at the start of the fight. During the cutscene you regenerate hatred, discipline and stack crit chance with sharpshooter.
If you take any hit you will die. Don't be afraid from dieing and if your resurrection timer is 30 seconds, make a short break like 3-5 minutes after you live again, to reset it. Use Smoke Screen as often as you are in danger. I died to often, because I want to safe some discipline.
Your templar starts to attack the monsters, use Smoke Screen and stand behind him on the left or right side. Then clear the first group very fast with Elemental Arrow. Then spam Hungering Arrow as long as the next group spawns. Then kill the nearest monsters with Elemental Arrow and use Smoke Screen if they come to close to you or to many monsters spawn on your side. Don't stand on an spawn point and spam Elemental Arrow all the time. You must learn where the monsters can spawn and how to handle this situation. In the beginning it's better to use Smoke Screen as often as you are in danger, because it's important to reach phase 2 to learn it.
After a short cutscene Belial joins the fight. Don't skip this cutscene. First use Marked for Death on him. Belial will charge you and use his cleave attack, use immediatly your smoke screen and go on range on him. Shoot Elemental Arrow on him. If he charges you again run away from him to dodge his cleave attack or to be safety use smoke screeen. Try to do as most damage as possible with Elemental Arrow.
After like 3 charges he shoots 3 green projectile at you. If you stand behind the templar and he eat the projectile focus on damage, if he doesn't eat a projectile dodge them. If you have him already at 50-60% use smoke screen and focus on damage to get him to 20-25% to start phase 3. Shortly after he shoots green projectiles, he summon monsters, which must be killed. Use Smoke Screen to get on range to them and kill them. Sometimes you can ignore the summoned monsters and focus on Belial if he is low enough.
Again a short cuscene, which you shouldn't skip. Now Belial is a stationary boss. At the start of the fight use Marked for Death on him and shoot Elemental Arrow. Green circles indicate where he attacks. If it's close to you use smoke screen and get some range. Continue to dodge his attack if the green circle is near you, but try to stay on the right side. If he starts using his breath go right edge of your screen so you don't get killed by his breath, if you aren't fast enough use Smoke Screen. Focus on damage by spamming Elemental Arrow. Depending on your damage and crit luck he will be very low before he uses his green meteor strike. Don't use Smoke Screen in this situation. IF you use it during the meteor strikes he will cast it randomly all over the place. Dodge it by moving and finish him off.
I got following achievements with my Solo Inferno kill.
Why'd It Have to be Snakes
beat 10 Veiled Sentinels in 30 seconds while fighting Belial on Nightmare or higher
beat Belial without being hit by his projectile or meteor strike
beat Belial on Inferno without being hit by his
beat Belial without being hit by his
Out of the Shadows
finish the Belial achievements Why'd It Have to Be Snakes, Good Eye Fist
Missed. Bad Breath.
The Lord of Lies (Inferno)
Have fun with Belial! Next step for me Inferno Act III.