In Matt 6:13, the Greek reads (in part)
- ἀλλὰ ῥῦσαι ἡμᾶς ἀπὸ τοῦ πονηροῦ. (= but deliver us from the evil [one]")
Interestingly, Luke 11:2-4 does not include this phrase.
The word πονηροῦ (ponerou) is a genetive Adjective, from the root word πονηρός (poneros) which simply means, "evil, bad, wicked, malicious, slothful" (Strong). BDAG gives several meanings for this, but the primary meaning is: "pertaining to being morally or socially worthless, wicked, evil, bad, worthless, vicious, degenerate".
It is used purely as an adjective in places like Matt 12:35, Luke 6:45, 2 Thess 3:2, 2 Tim 3:13, etc. It is also used substantively in: Matt 5:39, 45, 13:49, 22:10, Luke 6:35, 1 Cor 5:13, etc, and (according to BDAG) also in Matt 6:13.
Thus, the operative phrase in Matt 6:13 should be rendered, "But deliver us from the evil one". (This presumably refers to the devil's temptations and influence.)
Now to the other part of the question about the text: Should the doxology, "for yours is the kingdom, the power and the glory for ever, Amen", be included or not? The facts are these (MSS dates in brackets):
Diatessaron (2nd) omit, cop(meg) (3rd) omit, Origen (3rd) omit, Tertullian (3rd) omit, Cyprian (3rd) omit, 01 (4th) omit, 03 (4th) omit, it(a) (4th) omit, syr(c) (4th) include, Cyril-J (4th) omit, Gregory-N (4th) omit, vg (400) omit, Ambros’r (400) omit, Ambrose (400) omit, it(k) (400) include, 05 (5th) omit, it(b) (5th) omit, it(h) (5th) omit, Cyril (5th) omit, Chromatius (5th) omit, Jerome (5th) omit, 032 (5th) include, syr(p) (5th) include, 0233 (500) include, 035 (6th) omit, 042 (6th) include, it(f) (6th) include, syr(p)al (6th) include, 0170 (500) omit, it(q) (600) include, it(aur) (7th) omit, syr(h) (7th) include, it(l) (8th) omit, 07 (8th) include, 011 (9th) include, 019 (8th) include, 037 (9th) include, 038 (9th) include, 33 (9th) include, 565 (9th) include, 892 (9th) include, 1424 (900) include, f1 (10th-14th) omit, f13 (11-15) include, l 547 (13th) omit.
Jerome's Latin vulgate (~400 AD) and the Clementine text omit the doxology. Thus it is absent from the DRB and modern Catholic Bibles. It is also absent from almost all of the church Fathers including Augustine.
The Doxology first appears in a Syriac translation. It first appears in Greek MSS in the fifth century but it is not until the 6th century that it appears more often. Even the high medieval text group, f1, does not include it. However, it is a favourite of the Byzantine set of MSS. (Note that both sets have variations within them.)
Bruce Metzger in his "Textual Commentary on the GNT" says of this section:
The absence of any ascription in early and important representatives
of the Alexandrian, the Western (D and most of the Old Latin, and
other (f1) types of text, as well as early patristic commentaries on
the Lord's Prayer (those of Tertullian, Origen, Cyprian), suggests
that an ascription, usually in a threefold form, was composed (perhaps
on the basis of 1 Chr 29:11-13) in order to adapt the Prayer for
liturgical use in the early church. Still later scribes add, "of the
Father and the Son and of the Holy Spirit".