The Evil Path Isn't as Unrewarding as People Say
I hear a lot of people say they can't do an evil run because of the items you're losing out on if certain npcs die. On one hand, they're right because Dammon sells arguably the best heavy armor in the game in act 3. But on another hand, there are a lot of items you can only get on an evil run that are very good as well.
Let's break this down by acts. I'll separate items you can get on the evil and good path, respectfully. This is not an exhaustive list, it's just to give perspective.
Act 1 Good Path Rewards & Items Sold by Good/neutral Aligned Traders:
Arron: Gloves of missile snaring, ring of flinging, spellthief.
Dammon: Safeguard shield
Volo: Whispering promise ring.
Rewards for saving the grove: Hellrider pride (you get this a little before completing the quest, but I'll include it). The wolf rune that lets you into an underground stash where you can find the robes of summer, and sorrow. The pale oak (only if playing as a druid). NOTE: You can loot the hellrider's pride and the wolf rune if you kill the grove.
Rewards for saving Florrick: Your choice of a lightning charge weapon. I always pick the spellsparkler, idk what the other items are called
Act 1 Evil Path Rewards and Items Sold by Evil Aligned Traders:
Auntie Ethel: Hill Giant Strength potions (refreshes after each long rest), Corellon's Grace (good for monks in the early game).
Grat the trader: Doom hammer, whispering promise ring, returning pike.
Roah Moonglow: Bow of awareness.
The Zhents: Titanstring bow, Harold, gloves of thievery, jolty vest.
Murder the Flaming Fists who are trying to save Florrick: Svartlebee's Woundseeker
Rewards for killing the grove: A tadpole (plus all lootables from the grove). All goblin leaders can still be killed for their tadpoles after raiding the grove (including Minthara). So killing the grove plus the goblin leaders will net you 4 tadpoles in total.
Rewards for killing Karlach: Infernal robe, sword of justice.
Rewards for selling out Mayrina: +2 stat bonus.
Act 2 Items (Good Path & Good/Neutral Aligned Traders):
Dammon: Darkfire bow, all helldusk equipment, charge-bound warhammer.
Talli: Shield of devotion, cloak of protection, Yuan-ti scale mail, the mighty cloth, amulet of the harpers, shadeclinger armour, incandescent staff.
Mattis: Evasive shoes
Barcus: Gloves of the automaton
Reward for saving the tieflings: Potent Robe
Reward for saving Wulbren: the brilliant retort.
Reward for saving Last Light: The Harpers help fight the guards at Moonrise later.
Rewards for saving Aylin: Selune's spear of night, moonlight glaive (both garbage in comparison to the rewards Shar gives, imo). Aylin also joins you in battle, but I feel like I have to support her, not the other way around.
Act 2 Items (Evil Traders & Rewards):
Araj: Risky ring, ring of free action, robe of exquisite focus, unique exlirs (if giving her blood samples), +2 to strength stat.
Roah: Drakethroat glaive, ne'er missile, marksmanship hat
Lann Tarv: Halberd of Vigilance, sentinel shield, fistbreaker helm, dwarven splintmail (if you persuaded Z'rell into letting you shop her secret stash. Stock refreshes once per long rest). Render of mind and body. Titanstring bow (if you didn't get it in act 1).
Killing Isobel: Jhannyl's gloves. Slayer form (if playing as Dark Urge).
Killing Aylin: Shar's spear of evening (better than Selune's alternatives imo).
Act 3 Good Items
NOTE: There's so much stuff going on in act 3. I'll only list items you get from the tieflings and the Bhaalist cult because I feel like they contrast each other pretty well.
Dammon: Armour of persistence, boots of persistence, legacy of the masters.
Echo of Abazigal (unlocked for the unholy assassin of Bhaal): Bhaalist armour, assassin of Bhaal cowl, craterflesh gloves.
Reward for saving Zevlor: Hellrider's paladins join in the final fight.
Reward for saving Rolan from Lorroakin: Rolan's firestorm is available for the final fight.
Reward for embracing Bhaal (if playing as the Dark Urge): You gain power word kill. During the final fight, you can cast stunning gaze. The roll requirement you need to achieve a critical hit is reduced by 2.
Final Thoughts
Obviously not all items are exclusive to a specfic path (you can have a run with the armour of persistence and the Bhaalist armour for example). But you are plenty rewarded for the evil path. For me, it hurts me to save Aylin because of how good Shar's spear is. Aylin's transformation is good, and I love that Shadowheart gets to heal. Losing out on Shar's spear still hurts.