The standard thing with "compare with other similar spells" won't cut it, I guess.
Well, lessee. Let's look at OD&D Magic-User's offensive combat spells since everything eventually builds off the powerlevel of that level 1-6 list. (Things get screwy at levels above that, since level 6 already includes fairly godlike things and then you add three levels more.)
>Level 1
The only combat spells are Protection from Evil, Charm Person, and Sleep.
The first is limited to protecting from evil creatures and only works on the magic-user, the second only works on a single man-sized critter - effectively "max 2HD". Sleep's famously powerful, but allows a save in the LBBs (presumably later changed to speed up play), rapidly loses effectiveness against higher-HD opponents, is is extremely random.
If you have to extrapolate from other rules (as you often do in OD&D), the rules for attacking sleeping dragons somewhat indicate that all you get is +2 to hit and a free melee round. This feels slightly more balanced than AD&D's "slain automatically at a rate of 1 per slayer per round", but go with whatever you want.
>Level 2
Phantasmal Forces, mainly. In the tradition of Chainmail, this is basically a somewhat limited summoning spell: you can create one creature, whatever you want, but it vanishes instantly on an AC9 hit, the damage it does is only real if it's not seen through, and the caster needs to concentrate. A really powerful spell, no doubt (duplicate a dragon, gg no re), but completely negated by simple countermeasures.
>Level 3
Hold Person is a short-duration Mass Charm Person, alternatively Charm Person +2.
Fire Ball and Lightning Bolt do LVLd6 damage in a large area at range.
>Level 4
Polymorph Others is a single-target save-or-lose, Wall of Fire/Ice are temporary battlefield control, Charm Monster is Person without limiters, Confusion is random battlefield control that's much less reliable against higher-level foes.