Thank you, I am glad it does <3

Yes, Lethal tempo is a viable option, along with press the attack and Conqueror.
However in this current meta, conqueror is recommended

Hi, i also play kindred, in my experience i dont really have mana issues. Ive also played when manamune kindred was meta, back 2 years ago or so

Hello Kid7Ink,
Thank you for your question.
As we are going for on hit damage, with the percentage damage Blade of the Ruined King gives, and the 24% armor reduction from Black Cleaver, Guinsoo's Rageblade helps you shred the enemy HP much faster with its 15% armor penetration and also gives you an extra on hit effect each third attack. Going for my build and buying Guinsoo's Rageblade maxes your attack speed to 2.5, and will just shred enemy bruisers and tanks very quickly (Specially the more stacks you get with Kindred). Even when I am behind, once I have Guinsoo's Rageblade I am able to carry team fights... it just synchronises very well with the on hit effects of Blade of the Ruined King & Black Cleaver.
Other option should only be build when the enemy team is more squishy, even tho my build would still perform well, it would also be liable to build Infinity Edge & Runaan's Hurricane but I personally always prefer building full on hit as I just get much more sustain and damage output and overall better performance, I would personally never build Crit as it doesn't suit my play style, but this is a personal choice and how people play Kindred.
If I really had to choose, I would build Youmuu's Ghostblade instead of Guinsoo's Rageblade.