Thresh is the only champion with zero armor growth per level — his projected level 18 armor ranks dead last among 173, under a third of the average

I went through all 173 champions one by one. Looking at armorperlevel — how much armor grows per level — only Thresh comes up zero. Every other champion has at least Gnar's 3.7, but Thresh sits at a flat, genuine 0 (I double-checked the data, thought it was a fetch error at first).

What this number actually is

ddragon's base champion data has two armor fields: armor (the level-1 value) and armorperlevel (growth per level). In-game, current armor is calculated by applying a per-level growth curve (0.7025 + 0.0175×(level-1), weak at low levels and ramping up toward 18) to that growth value. The bigger armorperlevel is, the more armor a champion gains as they level.

Thresh is the only one who never moves

Sorted from the bottom, Thresh's 0 is completely isolated in last place, with a 0.7-point gap before the next entry, Gnar. The roster average is 4.54, clustering around 4.7 (40 champions) and 4.2 (34 champions). The top is a tie between Sejuani and Hecarim at 5.45.

Champion	Armor growth
Thresh	0
Gnar	3.7
Sejuani	5.45
Hecarim	5.45

The same pattern holds even within his own role

Averaging by role tag barely moves the needle: Fighter 4.65, Tank 4.56, Mage 4.53, Support 4.51, Assassin 4.51, Marksman 4.41 — every role sits in the same 4.4-4.7 band. Other Support/Tank-tagged champions like Lulu (4.6), Nami (5.2), Soraka (5), and Braum (5) all fall neatly inside that range too, so role doesn't explain it. Thresh is the outlier even among his own archetype.

The gap only widens at level 18

Applying that growth curve to estimate level-18 armor, the roster average lands around 107. Since Thresh's growth value is zero, his armor stays at his base 33 no matter the level — dead last among all 173. That's under a third of the average, while even Gnar, the second-lowest, climbs to nearly half the average. Thresh is the only one left standing at the starting line.

Collecting souls instead of growing with levels

I don't think this zero is a bug — it reads like a deliberate design choice. Thresh's passive, Damnation, permanently grants armor and magic resist every time he collects a soul from a nearby death. It looks like the automatic per-level growth other champions get for free was deliberately stripped out and replaced with player action (soul collecting). Where his armor comes from is fundamentally different from the other 172, who just get stronger by leveling up.

Takeaway

Looking at ddragon's numbers alone, Thresh has the weakest armor growth in the game, but his actual tankiness in a match is decided by how many souls he's collected. That zero on the stat page is numerical proof that he's built to get stronger through play, not through leveling.

A flat zero that still works as a tanky support — you'd never guess it from the stat sheet alone