Which Android phone is best under the range of 15k?

Well I live for giving short answers :P

I will make it short and simple and under 15k your following options should be:

Redmi Note 4

Pros:

• Awesome battery life probably the best in this segment
• 2.5D curved glass which makes the phone look more beautiful
• Snapdragon 625 which is power efficient

Cons:

• Camera is decent, not awesome
• Processor is Snapdragon 625 might not handle the bestest of graphics smoothly

Huawei Honor 6x

Pros

• Awesome dual camera, quite good at low light
• Processor is Kirin 655 whose processing power is better than SD 625

Cons

• Battery life is a problem

Coolpad Cool 1 Dual (Made by 2 companies- Coolpad and LeEco)

Pros

• Awesome dual camera
• Processor is SD652 which is far better compared to Kirin 655 or SD625
• Battery life is also awesome

Cons

• Might or might not receive future updates as coolpad and leeco are currently not doing good in the market

Lenovo Zuk Z2

Pros

• Processor is SD820, the best processor in this segment(This is the same processor which is there is MI5 and OnePlus 3)
• Camera is good, better than Redmi Note 4
• Compact phone of 5inch screen so its good for one hand usage

Cons

• Will not receive any future updates(officially confirmed from Lenovo). This recently got Nougat update which still many phones don't have, so you can still go for it if you want the fastest mobile in this segment

Moto G5 Plus

Pros

• The bestest of camera in this segment with dual autofocus which is best to capture every detail even in very low light conditons
• Processor is SD625(Same as Redmi Note 4) power efficient

Cons

• Battery life is OK, not way too good nor way too bad

Choose the one as per you desire

In this post many other people have recommended many other phones. Don't ever think about them as they are not the best ones

Glad to help you