Diablo II: Resurrected

Only requires a Normal playthrough. Achievement pops after baal kill. Get a squad to protect and compliment everyone or a high level person to carry you if you want to cheese it. If playing solo just pick a class with good low level strengths (summon necro, trap assassin, barb, holy fire/freeze paladin, etc). Invest more into resists, defense, vitality and block than you otherwise would and go slow. Repeat areas to over level yourself before trying to move on. Once you hit level 20 for ancients you can complete baal quest - again, easiest if someone rushing. If you are walking you should be above level 16 after completing act 2. Replay tombs until you hit 24 and continue on the rest of the game. Should get you close to 30 by the time you fight baal and strong enough to win.