Vishnu

 This is Tandav shanmukh strotra in siddh nagarjun tantra

करालदंष्ट्रवदनमत्युत्तममहाविभुम् ।
कालरात्रिसुतं विष्णुं प्रलयाग्निसमप्रभम्

Here lord kartikeya is called Vishnu means kartikeya is non different from Vishnu so don't believe on so called sectarians.

This is another evidence

ॐ रं नमो भगवते - महासेनाय -
विष्णुतुल्यपराक्रमाय - अग्निप्रळयमयूरताण्डवेश्वराय -
सहस्रदिङ्मुखाय - सहस्रत्रिनेत्राय -
शतकोटिकपालमालालङ्कृताय - शार्दूलचर्माम्बरधराय -
द्विसहस्रकोटिखड्गखेटककटकधराय - मां रक्ष रक्ष -
मम शत्रून् जहि जहि - छिन्धि छिन्धि - भीषय भीषय ह्स्रों

If they are not equally powerful then why Lord Kartikeya is said to be Vishnutulya parakramay means equal to Vishnu in power or strength. 

One more evidence Kartik is a month similar to Kartikeya this month is also known as Damodar mass a name of Vishnu.

Here Damodar(Krishna) and Kartik (Kartikeya)are same month.

https://www.google.com/search?q=kartikeya+Vishnu