Open the Engine.ini file from : "C:\Users\YourUserName\Saved Games\CrimeBoss\Steam\Saved\Config\WindowsNoEditor" and add these lines at the bottom :

[SystemSettings]
r.TemporalAA.HistoryScreenpercentage=200
r.BasePassForceOutputsVelocity=1
r.DefaultFeature.AntiAliasing=2
r.TemporalAAPauseCorrect=1
r.TemporalAA.Upsampling=1
r.TemporalAACatmullRom=1
r.TemporalAA.Algorithm=0
r.TemporalAASamples=4
r.PostProcessAAQuality=6
r.AntialiasingMethod=2
r.TemporalAA.Quality=2
r.VelocityOutputPass=1
foliage.DitheredLOD=1
r.Tonemapper.Sharpen=0
r.SceneColorFringeQuality=0
r.MotionBlur.Amount=0
r.MotionBlurQuality=0
r.Tonemapper.GrainQuantization=0
r.DepthOfFieldQuality=0

[/script/unrealed.cookersettings]
+VersionedIntRValues=r.VelocityOutputPass





What do these lines do?!

-TAA : Makes it cleaner, less prone to ghosting and on average, has improved temporal stability, at a performance cost, nothing too drastic but that'll depend on your GPU, it performs about 3-4% worse than the "Default TAA" setting on my specs on average, however it's night and day in terms of quality and sharpness.

-"r.TemporalAASamples=4" Modify this line if you want less or more aliasing, 2 is a good alternative for sharpness up to 8 / less=sharper - more=smoother, i personally use 4, 1 is the sharpest but can have issues on static scenes and in other circumstances.

-If you want to reduce noise and light flickers, use the denoising lines from the link below, usually the bloom related line is enough to "fix" the issues with light flickers.

-Disables Chromatic Aberration, no description needed, it disables CA.

-Disables Depth of Field, same as above, although ADS seems unaffected as it's probably blur and not actual DoF.

-Disables Motion Blur, yes you can turn it off in game too.

-Disables Film Grain, if there's any.

-You can tweak the r.Tonemapper.Sharpen= value if you want more or less sharpening, for me in Crimeboss these settings are fine, but your experience may vary.

You can modify and experiment with these as you wish, these lines can also be used and applied to any UE4 and UE5 games, although for UE5 i would suggest using TSR settings instead.

Presets for further TAA modification are listed in the guide by TheHybred in the link below, this guide's settings keeps the game's default TAA samples, Filter size and frame weight, feel free to check by yourself which presets give the best results for you.

===2025 Update===
If you have an Nvidia GPU, i highly recommend using DLSS with the lastest dlls and setting the preset to K/Latest, either for DLAA/Native or quality mode and lower.
You can change the preset either with the Nvidia app, or with Nvidia Profile inspector, which i would recommend instead.

Source :
TheHybred for his great guide on TAA for UE4/UE5 games, he also makes mods that improve TAA amongst other things.

https://www.reddit.com/r/OptimizedGaming/comments/18615sh/best_ue45_antialiasing_values