There are passages that have been, in some sense, "removed" from the bible. There are things that may have been censored to avoid allusions to polytheistic worship. For instance, there's a passage (Deuteronomy 32:8-9) which, in the Septuagint (an early translation to Greek of the Hebrew bible) and the Dead Sea Scrolls (early fragmentary biblical manuscripts) say something like:

When Elyon divided nations, and separated peoples, he set up the borders of nations, according to the Sons of God. The portion of YHWH is his nation, Jacob is his inheritance

Whereas the standard Hebrew text reads:

When Elyon divided nations, and separated peoples, he set up the borders of nations, according to the Sons of Israel. The portion of YHWH is his nation, Jacob is his inheritance

There are generally speaking more textual witnesses to the first reading. Combined with other passages with similar references, the former reading seems to reference monolotry, not monotheism, a time when Israelites believed in the existence of the Canaanite pantheon, but they were to exclusively worship one god, YHWH. In this conception Elyon "assigned" YHWH to Israel. This would've been potentially unacceptable to later readers, who would've redacted the verse to sort-of make sense without the problematic theology. There are more examples, such as later in that same chapter a possible redaction of mention of divine beings besides YHWH. Unlike the previous one, which is redaction, not removal, short passages seem to have actually been omitted from the standard Hebrew text.

Another emendation to the bible are the tikkunei soferim. These are instances where the biblical text has the opposite word from what is intended, to avoid the bible containing a theologically offensive phrase, but where the meaning was to be understood in an offensive way. Stuff like changing "curse God" to "bless God". Rabbinic commentators made lists of these, but it's not clear exactly what's a scribal error and what's intended as a euphemism and what's just another understanding. There are various lists of them here. For instance, Genesis 18:22 in the standard text (and the LXX) has a group of messengers of God leaving Abraham, but "Abraham still stood before YHWH", which some commentators suggest was originally "YHWH still stood before Abraham", which uses potentially uncomfortable anthropomorphism. YHWH standing makes a bit more sense, since the messengers leave but Abraham keeps talking to God--contrasting YHWH standing while Abraham goes makes a bit more sense. But, there's no textual evidence of the YHWH standing reading, and the other one makes sense too. It could also have just been a scribal error. There are more scribal error-y things, that could just be commentators finding ways to pick the obvious reading, such as messing with pronouns. Since Rabbinic commentators generally do not believe in scribal errors, they sometimes debate whether a passage makes sense as-is or if it's a tikkun soferim. In 1Kings 12 (and 2 Chronicles 10), for instance, the text has the Israelites "returning to their tents", which some commentators think is a euphemism for "returning to their gods" (this is similar-sounding in Hebrew), even though "tents" makes more sense contextually.

There are more clear-cut examples--references to God being angry at people "cursing themselves" (meaning "curse me", i.e. God himself. This is a less easy scribal error than general pronoun-messing in Hebrew). There are others that are not formally termed tikkunei soferim, such as "bless God" when contextually it's "curse God" (1Kings 21:13). Most translations have "curse", though it doesn't seem to be in the formal lists of tikkunei soferim (it may've simply been commented on as a euphemism--euphemisms to say the opposite of what you mean, particularly with bless/curse, are very common in Rabbinic texts and could have been seen as a euphemism, not an emendation). Another is changing the name of Saul's son from Ish-Ba'al (man of Ba'al, a Canaanite deity) to Ish-Bosheth (man of shame), to reference the shamefullness of his idolatrous name without needing to actually write it. The bible inconsistent about which to call him.

All of those possible emendations are about theological issues concerned with monotheism, not violence.

There are books that were, at one point, considered canonical by some (or they predated a fixed concept of a canon), that are now often left out of bibles. The concerns with these have to do mostly with authorship and worthiness of being scriptural, not violence. The only example of the opposite is that it has been suggested that part of the reason Maccabees was left out of the Hebrew canon is that in an era following violent (failed) Jewish revolts against the Romans, positively retelling a violent revolt was painful, politically dangerous, or otherwise bad. But there are other reasons for its exclusion, such as its late authorship (Daniel is late, too, but it's set in an earlier era, whereas Maccabees is not) or other political concerns (dislike of the Hasmoneans). That's pretty much the only example of a violent text being possibly removed, and it's very much speculative.

That one example specifically is possibly removed because the text is about violence in a politically/socially unacceptable way, not violence itself. There are loads of violent texts in the bible, sometimes very violent ones. Violence itself does not seem to have been a huge issue for biblical authors or redactors.

Removed by who? Are you asking if Canonical books were later censored by somebody or whether something was removed from earlier source material during the composition process, or whether there was some kind of intermediate editing between composition and canonization?