One idea - Melf's Minute Meteors - from 3th spell slot it's 12d6 dmg with 10 ft diameter. With use on enemy with Hex and Hexblade curse (some boss with huge amount of HPs, because you need 3 rounds to get in use) it's 12d6 fire+6d6 necro+6xProficiency, for every higher slot it's +4d6 fire + 2d6 necro + 2x Prof
negatives? - You can send only 2 meteors per round by bonus action (cant use quckened spells, or when move Hex), So useable for fights with more rounds.
But needn't use meamagic and spellpoints for use actions and bonusactions to deal dmg to enemy...
On 5th lvl:
1. round - BA - Hex, A - EB // 2d10+2d6+8(AgonizingB)
2. round - BA - Curse, A - EB // 2d10+8 +2d6 +6 (2x proficiency)
3. round - A - MMM, BA - send 2 meteors // 4d6 +2d6 +6
4. round - A - EB, BA - send 2 meteors. // 2d10+8 + 4d6 + 4d6 +12 = 59 Dmg before attack/save but no other spellslot and spellpoints... (and those 4d6 fire can be used for 4 creature when they are standing close)