Max ability ranks add up to exactly 18 for 166 of 173 champions. Udyr alone has all four at 6, totaling 24

I lined up all 692 abilities across 173 champions, four slots each for Q, W, E and R, and counted only their max ranks. Basic abilities cap at 5, ultimates at 3. That's the template for nearly everyone, and 5+5+5+3 adds up to 18, exactly matching the level cap of 18. 166 of 173 champions, 96%, land on exactly 18.

The remaining seven are where it gets fun.

What a max rank actually is

In League you get one skill point per level and spend it to rank up one ability. Ultimates can only be ranked at levels 6, 11 and 16, so a normal champion ends up with every ability maxed right at level 18. Flip that around: any champion whose max ranks don't sum to 18 is doing something unusual with skill points.

Only seven exceptions

Of the 519 Q/W/E abilities, 10 don't cap at 5. Of the 173 ultimates, 5 don't cap at 3. That's 15 abilities total, grouped by owner below.

Champion	Q	W	E	R	Total
Udyr	6	6	6	6	24
Aphelios	6	6	6	3	21
Jayce	6	6	6	1	19
Yuumi	6	5	5	3	19
Elise	5	5	5	4	19
Karma	5	5	5	4	19
Nidalee	5	5	5	4	19

The three with a 4-rank ult start with it

Elise, Karma and Nidalee have ultimates that cap at 4. All three can transform or use Mantra from level 1 (Karma's R description in ddragon even says Mantra is available at level 1 and doesn't require a skill point). That first rank comes free, so a total of 19 still fills up perfectly with 18 points. Makes sense.

Jayce's R has a single rank

Jayce's ultimate caps at just 1. Swapping between hammer and cannon is available from level 1 and never improves after that. Instead his Q, W and E go up to rank 6, so 6×3 means all 18 points pour into his basic abilities. Among transforming champions, there's a clean split: Elise and Nidalee level their R, Jayce doesn't.

Aphelios's Q/W/E aren't normal abilities

Aphelios also has three abilities capped at 6. But his E description says he has no third ability and the slot just shows the next weapon in line. Putting skill points in raises his stats rather than an ability, so I think those 6 ranks exist purely as a place to spend points (I'm a noob and never once wondered what leveling Aphelios's E actually did). A total of 21 can't be filled with 18 points.

Yuumi has one extra Q rank

Yuumi's Q caps at 6 while her W and E stay at the usual 5. That makes 19, but ddragon's descriptions don't explain where the extra point comes from. Honestly, I don't know on this one.

Udyr can never max everything

Last is Udyr. All four of his abilities cap at 6, and his total of 24 beats Aphelios's 21 for the most among 173 champions, about 1.33x the standard 18. Udyr's R isn't a normal ultimate but another stance on equal footing, and his passive describes him as having four basic abilities. With 18 points for 24 ranks, maxing everything is impossible. Since 6×3 is 18, you can max at most three of the four. Which one you leave behind basically defines your Udyr.

Takeaway

Out of 692 abilities, only 15 break the textbook max rank, owned by just seven champions. Those seven mostly fall into one of four buckets: R from the start, R that never grows, skill points with an unusual purpose, or a kit you simply can't fully max. Max ranks look like boring numbers, but this is exactly where champion design shows through most honestly.

So Udyr was built from day one with 6 ranks meant to be left on the table…