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Kiss up, kick down is a popular ism for people who boot lick upward and kick their subordinates but What would you call some one who typically kisses horizontally i.e. inter departmental equals. but kicks any and all below them.

You are basically describing somebody who is being excessively nice to all persons at his own power level and above, and simultaneously ruthless towards anyone below that power level.

"Kiss up, kick down" is already a legitimate expression and social phenomenon which has its own page on Wikipedia:

Kiss up kick down (or suck up kick down) is a neologism used to describe the situation where middle level employees in an organization are polite and flattering to superiors but abusive to subordinates. It is believed to have originated in the US, with the first documented use having occurred in 1993.

Source: https://en.m.wikipedia.org/wiki/Kiss_up_kick_down

What you describe as "kisses horizontally" is just an extension of that "kiss up" behavior. The kisser is probably following the mathematical principle of "greater than or equal to" out of insecurity or to gain maximum benefit.

Persons who resort to flattery of powerful or influential people to gain favors have long been described by words like 'sycophant', 'courtier' or 'flatterer.'

"Curry favor" in British English describes the act of ingratiating oneself with superiors.

Source: https://www.collinsdictionary.com/dictionary/english/curry-favour

There are a number of vulgar terms for someone who curries favor with real or perceived higher-ups, none of which is decent enough for me to include explicitly here. Covert mention: one who kisses a donkey, or an expression related to the color of one's nose.

Somebody who 'kisses up horizontally' to inter-departmental equals is probably being simply insecure. They are trying to win co-operation, popularity and acceptance through flattery [ I know all about it, I did it myself for 2 years in 2010-12 as a green young public official thrust into a senior post.] As for the 'kicking down', I have never done it myself but that sort of person is often perceived as an exploiter// ruthless and spineless // a coward.

But the combination of these ideas is what you seek... rather more than literally accurate meanings, we have words that show what others think of such a person. A good figurative fit from British slang seems to be rotter which is commonly defined as a thoroughly bad, objectionable or worthless person.

Sources: https://www.merriam-webster.com/dictionary/rotter

http://www.dictionary.com/browse/rotter

Such a person may also be called a "bad egg" which means an unreliable, dishonest or good-for-nothing person. This is apparently an Americanism dating back to 1850–55.

Source: http://www.dictionary.com/browse/bad-egg

Here in India, such a person might be described from the 'kicked' subordinates' perspective as "a self-serving, cunning and useless person." Some Indians will even make "useless" into a derogatory noun:

"He kisses up to authority but insults and neglects his subordinates: he is a useless!"

If you like to use alliteratively ironic juxtapositions, I came up with the semantically accurate expression 'tyrannical toady' where 'toady' refers to the kissing up and 'tyrannical' refers to the kicking down. Cambridge dictionary defines 'tyrannical' as exercising unfair power over other people, and 'toady' as a person who praises people in authority to get advantages from them.

I later did a google search and found that "tyrannical toady" has been used exactly twice before: which at least documents the expression.

Notable example of previous use:

As for Penguin, his characterization takes after his Pain and Prejudice incarnation. He's a simpering cowardly backstabbing power hungry tyrannical toady (...) he's an amazing character. __ by user @anonymous on https://4archive.org/board/co/thread/85080208, emphasis mine.

'Tyrannical toady' is not nearly so potentially obscure or confusing a phrase as for example, "discombobulating prestidigitator" (whose meaning I had to look up one piece at a time, when an English-loving uncle used it to covertly and obscurely call another relative a manipulative trickster), but still: if you are very lucky, nobody will understand what you meant.

If someone only seeks friendships for ulterior benefits, I'd call them a schmooze or schmoozer.

Both are noun versions of the Yiddish verb schmooze:

To talk casually, especially in order to gain an advantage or make a
social connection.

It has a slightly derogatory tone which could imply their contempt of those beneath them.

I wanted to answer with "upwardly mobile" (as used in a sarcastic sense), but it seems like the "person" you describe is not indulgent toward those above them. But, in the same sense, you could coin a related phrase like "sidewardly mobile" or "awkwardly mobile" (because either promotion or demotion would probably end in disaster). I think people should get what you mean. You could probably use both of them for a more specific or nuanced effect, and you might even be able to use "eastwardly" and "westwardly" without ambiguity as well.

https://www.thefreedictionary.com/upward

https://www.thefreedictionary.com/sideward

https://www.thefreedictionary.com/downward

https://www.thefreedictionary.com/awkward