Here's the fact: Zero point nine nine nine with infinitely limitlessly increasing nines will never, EVER be one.

No buts about it.

If youS try to deny this basic fact, I strongly suggest for youD to get on the bunny slopes before I force, youS to.

Start with zero point nine, then zero point nine nine, then zero point nine nine nine, then zero point nine nine nine nine, then zero point nine nine nine nine nine, then zero point nine nine nine nine nine nine, And keep going like that until you finally discover the truth, behind zero point nine repeating, and learn that it will permanently, forever, be less, than one.

I will give youS your next task after youS complete that task.

Aaand begin!

Merriam-Webster:

boner, noun, bon·er

1 : one that bones

2 : a clumsy or stupid mistake

also : howler sense 2

The Ever-Bulging List

(Because we all need protection from the most hardened denier.)

1. The Irrational Boner: 0.999... is rational. 0.999... is not rational. (1.1) (1.2)
2. The Definitional Boner: 0.999... is eternally less than 1. It's fine if 0.999... is defined as 1. (2.1) (2.2) (2.3)
3. The Remainder Boner: In polynomial long division of a/(1-r), the remainder term goes away, or doesn't go away, at your convenience (e.g. 1/9 = 0.111... or 0.111...1 + 0.000...1/9 but 9/9 = 0.999... + 0.000...1 or 0.999...9 + 0.000...1). (3.1) (3.2) (3.3)
4. The Limbosic Integer Boner: A limbosic number can't be an integer. Some limbosic numbers are integers. (4.1) (4.2) (4.3)
5. The Infinite Long Division Boner: In long division of infinite decimals, you may consider truncations of the dividend in sequence in whatever way is convenient, and you may get different answers (e.g. 0.333.../2 -> 0.1, 0.16, 0.166, ... or 0.15, 0.165, 0.1665, ...). (5.1) (5.2)
6. The Unreal Boner: 0.999... is not a real number. 0.333... is a real number, and therefore 0.999... is a real number. (6.1) (6.2)
7. The Infinite Sets Boner: There is no static, infinite set of all natural numbers, but there is a static, already extant, infinite set of decimals of the form {0.9, 0.99, 0.999, ...}, even though that set maps to a static, infinite set of all naturals. (7.1) (7.2) (7.3)
8. The Greater Boner: Limbosic numbers do not have fixed values and can't be compared via (in)equality to any number within the range they span. Nevertheless, even though 0.999... is a limbosic number, 0.999... > 0.99. (8.1) (8.2) (8.3)
9. The Static and Dynamic Boner: There is a static model of 0.999... and a dynamic model. 0.999... is not static. It is dynamic. (9.1) (9.2)
10. The One-Third Boner: 1/3 is a number "of course". Multiplying a number by its reciprocal is divide negation (e.g. 1/3 x 3 = 1). 1/3 is not a number. (10.1) (10.2) (10.3)
11. The Slots Boner: 0.999... is a number with all decimal place slots to the right of the decimal point filled with 9s. To suggest 0.999... is a number with all decimal place slots to the right of the decimal point filled with 9s is to suggest there is an "end" to the 9s and therefore "nonsense". (11.1) (11.2)
12. The Infinite Integer Boner: There is no such thing as an infinite integer. 10... is one of infinitely many infinite integers. (12.1) (12.2)
13. The Integer Number of Nines Boner: The number of 9s in 0.999... is infinite. The number of 9s in 0.999... is always an integer. (13.1) (13.2)

Honorable Mentions from the Stiff Competition

FernandoMM1220's Boner: pi is always rational

Please feel free to suggest other massive boners from His Nineliness or others.

Give me ‘em all