Sona can't take half of anyone's HP at level 1 with her burst. Even Anivia without runes or masteries can take a fully offensive level 1 Sona burst.
Anivia's base stats:
Sona with offensive runes and masteries:
- Base Attack Damage: 50.04
- Masteries
- Double-Edged Sword (Ranged): +1.5% damage
- Expose Weakness: Allied damage +1% upon being hit by damaging ability
- Brute Force 3/3: 9.9 attack damage
- Mental Force 3/3: 16.02 ability power
- Spell Weaving: Basic attacks increase ability damage by 1%, stacking up to 3 times
- Martial Mastery: 4 attack damage
- Arcane Mastery: 6 ability power
- Executioner 3/3: +5% damage to champions below 50% health
- Blade Weaving: Damaging an enemy champion with an ability increases basic attack damage by 1%, stacking up to 3 times (stacks limited to 1 per second)
- Warlord 3/3: +5% Bonus attack damage
- Archmage 3/3: +5% Ability power
- Devastating Strikes 3/3
- +6% armor penetration
- +6% magic penetration
- Arcane Blade: Basic attacks deal 5% AP bonus magic damage
- Havoc: +3% damage
- Runes
- Marks: 9 x Greater Hybrid Penetration
- 9 x 0.9 armor penetration = 8.1 armor penetration
- 9 x 0.62 magic penetration = 5.58 magic penetration
- Glyphs: 9 x 1.19 ability power = 10.71 ability power
- Quintessences: 3 x 4.95 ability power = 14.85 ability power
- Equipment
- Spellthief's Edge
- 5 ability power
- Tribute: damaging abilities and autoattacks to champions/structures expend charges to deal 10 bonus damage; damage type matches triggering attack
- Total Ability Power: 55.209
- Total Attack Damage: 64.635
- Total Armor Penetration: 6% | 8.1
- Total Magic Penetration: 6% | 5.58
Anivia's defensive stats after Sona's penetration is applied:
- Health: 467.6
- Armor: (21.22 x 0.94) - 8.1 = 11.8468
- Physical Damage Multiplier: (100 / 111.8468) = 0.89408*
- Magic resistance: (30 x 0.94) - 5.58 = 22.62
- Magic Damage Multiplier: (100 / 122.62) = 0.81553*
** Rounded to 5 decimal places*
Sona's damaging abilities:
- [Q] Hymn of Valor
- Direct damage: 40 + (50% AP) magic damage
- On-hit bonus: 20 + (20% AP) magic damage
- Power Chord
- 13 + (20% AP) magic damage
- +40% if charged with Hymn of Valor
So let's see what happens when we put this all together, shall we?
- Hymn of Valor initial damage: 40 + 27.6045 = 67.6045 magic damage
- Spellthief's Edge: 10 magic damage
- Expose Weakness: Subsequent damage +1%*
- Blade Weaving: Subsequent basic attack damage +1%**
- Autoattack: (64.635 x 1.01) x 1.01 = 65.9341635 physical damage
- Spellthief's Edge: 10 x 1.01 = 10.1 physical damage
- Arcane Blade: (55.209 x 0.05) x 1.01 = 2.7880545 magic damage
- Hymn of Valor (On-hit): (20 + 11.0418) x 1.01 = 31.66574018 magic damage
- Power Chord (Hymn of Valor): ((13 + 11.0418) x 1.4) x 1.01 = 33.9951052 magic damage
- Physical Damage Subtotal: 76.0341635
- Magic Damage Subtotal: 146.05339988
** I'm not sure if Expose Weakness applies to on-hit/on-ability effects triggered by the same action, so I'll assume it doesn't.*
*** I skipped some calculations for this. The Warlord mastery amplifies bonus AD, so it would get a larger boost. The difference is miniscule, though.*
When applied to Anivia's defenses:
- Physical damage: 76.0341635 x 0.89408 = 67.98062*
- Magic damage: 146.05339988 x 0.81553 = 119.11093*
*Rounded to 5 decimal places
And I haven't forgotten Double-Edged Sword and Havoc:
- Physical damage: 67.98062 x 1.045 = 71.0397479
- Magic damage: 119.11093 x 1.045 = 124.47092185
Alternately, this burst with Executioner on an under 50% health target:
- Physical damage: 67.98062 x 1.095 = 74.43878
- Magic damage: 119.11093 x 1.095 = 130.42646835
TL;DR
A foolishly built, purely offensive Sona at level 1 can poke the lowest health champion with no runes, masteries, or equipment for the following amounts:
- Full health target: 195.51066975 (41.8%)
- Target below Executioner threshold: 204.86524835 (43.8%)
In other words, Sona absolutely does not have a half HP level 1 uncounterable poke. Anyone who builds Sona this way is an easy target. Anyone playing without defensive runes has no leg to stand on regarding enemy pokes. Just having 9 flat MR Glyphs starts every champ at 30% magic damage mitigation.